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Multiple choice question for engineering

Set 1

1. The measure of the body’s resistance to angular acceleration is called ___________
a) Mass moment of inertia of a body
b) Volume moment of inertia of a body
c) Line moment of inertia of a body
d) Gauss moment of inertia of a body

View Answer

Answer: a [Reason:] The measure is known as mass moment of inertia of a body. It’s very useful in the designing of the structures. It also helps in the determination of the strength of the body. Thus a very useful thing in the structural engineering.

2. Determine the mass moment of the area of the cylinder given below.

engineering-mechanics-questions-answers-mass-moment-inertia-q2

a) 0.5mR2
b) 5mR2
c) 0.2mR2
d) 0.7mR2

View Answer

Answer: a [Reason:] The measure of moment of inertia of a body is important. It’s very useful in the designing of the structures. It also helps in the determination of the strength of the body. Thus a very useful thing in the structural engineering.

3. We define the moment of inertia of a body as________
engineering-mechanics-questions-answers-mass-moment-inertia-q3

View Answer

Answer: a [Reason:] The definition of the of the moment of the inertia of the body is given by engineering-mechanics-questions-answers-mass-moment-inertia-q3-1 That is the integration of the total mass and the square of the distance of that mass from the axis of rotation. Thus the moment of inertia.

4. Two of the things of the composite materials are to be known so that their mass moment of inertia can be varied. Which of the following is one of them?
a) Weight of the centre of gravity
b) Weight of the body
c) Location of the centroid of gravity
d) Location of the centre of mass

View Answer

Answer: b [Reason:] The centre of the gravity’s location and the weight of the composite body is needed to be known. This means that if both of the quantities of the composite body is known then the moment of inertia of the body can be altered. Thus both are very important things to be known about the composite bodies.

5. We define the moment of inertia of a body in terms of volume of the body as______________
engineering-mechanics-questions-answers-mass-moment-inertia-q5

View Answer

Answer: a [Reason:] The definition of the moment of the inertia of the body in terms of volume is given by engineering-mechanics-questions-answers-mass-moment-inertia-q5-1 That is the integration of the total mass as determined by the product of the volume and density and the square of the distance of that mass from the axis of rotation. Thus the moment of inertia.

6. We use the distance of the axis and the particles, and in that we apply parallel axis theorem. The distance in the parallel axis theorem is multiplied by_______
a) Area
b) Volume
c) Linear distance
d) Area/Volume

View Answer

Answer: a [Reason:] Parallel axis for any area is used to add the two mutually perpendicular moment of inertias for areas. It gives a moment of inertia perpendicular to the surface of the body. And uses the square of the distance from the axis of rotation multiplied by the area.

7. One of the use of the centre of mass or centroid is as in the mass moment of inertia is that the net force acts at the ___________ of the loading body.
a) Centroid
b) The centre axis
c) The corner
d) The base

View Answer

Answer: a [Reason:] In the moment of inertia calculations we see that the net force acts at the centroid of the loading body. That is if the loading system is in the form of the triangle then the at the distance 2 by 3 of the base the net force of the loading will act. And the load will be half the area of the loading.

8. If the non-Uniform loading is of the type of parabola then for calculating the mass moment of inertia for areas?
a) The net load will not be formed as all the forces will be cancelled
b) The net force will act the centre of the parabola
c) The net force will act on the base of the loading horizontally
d) The net force will act at the centroid of the parabola

View Answer

Answer: d [Reason:] The net force will act at the centroid of the parabola. Whether it be a parabola or the cubic curve the centroid is the only point at which the net force act. Force can’t be acted horizontally if the loading is vertical. Hence whatever be the shape of the loading, the centroid is the point of action of net force. Thus the use of centroid.

9. Determine the mass moment of the area of the cylinder given below.

engineering-mechanics-questions-answers-mass-moment-inertia-q9

a) Iz= 0.5mR2
b) Iy = 0.5mR2
c) Iz = 0.2mR2
d) Iy = 0.7mR2

View Answer

Answer: a [Reason:] The measure of moment of inertia of a body is important. It’s very useful in the designing of the structures. It also helps in the determination of the strength of the body. Thus a very useful thing in the structural engineering.

10. Which of the following is true?
engineering-mechanics-questions-answers-mass-moment-inertia-q5

View Answer

Answer: a [Reason:] The definition of the moment of the inertia of the body in terms of volume is given by engineering-mechanics-questions-answers-mass-moment-inertia-q5-1 That is the integration of the total mass as determined by the product of the volume and density and the square of the distance of that mass from the axis of rotation. Thus the moment of inertia.

11. The body is sometimes acted by two or three force members and we need to find the mass moment of inertia for the same. The difference between the two and the three force members is:
a) The former is collinear and the latter is parallel
b) The former is parallel and the latter is perpendicular
c) The former is perpendicular and the latter is collinear
d) The former is acting on two points in the body while the latter is on three points

View Answer

Answer: d [Reason:] The definition of the two force member only defines that the forces are being acted on the two points on the body. So does is the definition of the three forces members. The points of action of the three forces are three.

12. If any external force also is applied on the structure and we are determining the mass moment of inertia then what should we consider?
a) The net force will act at the centroid of the structure only
b) The net load will not be formed as all the forces will be cancelled
c) The net force will act on the base of the loading horizontally
d) The net force will not to be considered, there would be a net force of the distribution, rest will be the external forces

View Answer

Answer: d [Reason:] The external forces are treated differently. They are not added by the force of the distributed loading. That is the force not only acts at the centroid always. It can be shifted also. Depending on the external forces. Thus the use of centroid or centre of mass.

13. If any external force also is applied on the distributed loading on which the mass moment of inertia is to be determined on the composite body then?
a) The net force will act at the centroid of the structure only
b) The net load will not be formed as all the forces will be cancelled
c) The net force will act on the base of the loading horizontally
d) The net force will not to be considered, there would be a net force of the distribution, and rest will be the external forces

View Answer

Answer: d [Reason:] The external forces are treated differently. They are not added by the force of the distributed loading. That is the force not only acts at the centroid always. It can be shifted also. Depending on the external forces. Thus the use of centroid or centre of mass.

14. Which of the following is true?
engineering-mechanics-questions-answers-mass-moment-inertia-q3

View Answer

Answer: a [Reason:] The definition of the moment of the inertia of the body is given by engineering-mechanics-questions-answers-mass-moment-inertia-q3-1 That is the integration of the total mass and the square of the distance of that mass from the axis of rotation. Thus the moment of inertia.

15. We use sometimes the measures to know the direction of mass moment of inertia. It is done by right handed coordinate system. Which is right about it for the composite bodies (consider the mentioned axis to be positive)?
a) Thumb is z-axis, fingers curled from x-axis to y-axis
b) Thumb is x-axis, fingers curled from z-axis to y-axis
c) Thumb is y-axis, fingers curled from x-axis to z-axis
d) Thumb is z-axis, fingers curled from y-axis to x-axis

View Answer

Answer: a [Reason:] As right handed coordinate system means that you are curling your fingers from positive x-axis towards y-axis and the thumb which is projected is pointed to the positive z-axis. Thus visualizing the same and knowing the basic members of axis will not create much problem.

Set 2

1. The joint in the trusses are generally formed by welding the materials at the ends of the trusses on a common plate. Which gives strength to the design. What is that plate called?
a) Gusset Plate
b) Ignified plate
c) Non-metallic plate
d) Gymnite plate

View Answer

Answer: a [Reason:] The joint in the trusses are generally formed by welding the materials at the ends of the trusses on a common plate. Which gives strength to the design. This plate is known as Gusset plate. This plate holds up various trusses that are being welded to it , to make the structure strong.

2. Find the force in the member RQ of the frame shown below.
engineering-mechanics-questions-answers-mcqs-q2
a) 707.1N
b) 500N
c) 505N
d) 784N

View Answer

Answer: a [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

3. Trusses lie in a single plane. And the calculations used to solve the forces are from vector math.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: c [Reason:] The loading is acting in a plane. Thus the calculations are done in 2D only. As the equations for 3D are different. Although the use of vectors can make our task easy but still 2D calculations are done for the trusses, as they are acting in a same plane.

4. The transmission of the load on a certain type of a structure follow as from stringers to floor beams and then joints. Determine the structure.
a) Truss
b) Beam
c) Pillar
d) Bridge

View Answer

Answer: d [Reason:] The transmission of the load on the bridges follow as from stringers to floor beams and then joints. This is because of the first the stringers come in contact with the force. Which gets distributed to them. Then comes the floor beams, which takes that distributed loadings.

5. When the bridges are extended over long routes or distance then a rocker or a roller is used at the joints. As when the temperature is raised the elongations and the contractions of the joints part are not much affected if the rollers and rockers are used.
a) True
b) False

View Answer

Answer: a [Reason:] The roller and the rockers take over the elongations and the contractions of the joints part. And thus help in stabilising the structure. Thus when the bridges are extended over long routes a rocker or a roller is used at the joints.

6. Find the force in the member RS of the frame shown below.

engineering-mechanics-questions-answers-simple-trusses-2-q6

a) 566N
b) 400N
c) 773N
d) 1090N

View Answer

Answer: b [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

7. There are no rules for the designing of the truss. But there are rules designing the bridges.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: b [Reason:] There are various rules used to design the truss. Like the loads must be at the joints only. The use of pin must be there in the joining of the trusses etc. Also the joints must be welded with a gusset plate. And the bridges are also having various rules for their design too.

8. A truss is facing a two force member and both of them are in the opposite directions. And the truss is in equilibrium. And both of them are getting away from each other.The forces are called?
a) Compressive forces
b) Tensile Forces
c) Parallel and collinear forces with same direction of heading
d) The rotational forces

View Answer

Answer: b [Reason:] If two forces are in the opposite directions. And are collinear too. Then the truss is getting a tensile stress. As the forces are trying to increase the length of the truss. Hence if the two force members are in such conditions the forces are tensile forces.

9. A truss is facing a two force member and both of them are in the opposite directions. And the truss is in equilibrium. And both of them are coming towards each other. The forces are called __________
a) Compressive forces
b) Tensile Forces
c) Parallel and collinear forces with same direction of heading
d) The rotational forces

View Answer

Answer: a [Reason:] If two forces are in the opposite directions. And both of them are coming towards each other. And are collinear too. Then the truss is getting a compressive stress. As the forces are trying to decrease the length of the truss. Hence if the two force members are in such conditions the forces are compressive forces.

10. Find the force in the member PR of the frame shown below.

engineering-mechanics-questions-answers-simple-trusses-2-q10

a) 566N
b) 400N
c) 773N
d) 1090N

View Answer

Answer: c [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

11. Truss cannot be acted upon three force members. Because the truss in a single plane.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: a [Reason:] The singular plane of the truss doesn’t mean that the trusses cannot be acted upon the three force system. They can be acted upon the three force system, possibility is that the forces might not be collinear or might be parallel to each other. But point is the trusses can be acted on the three force members too, still conditions need to specific.

12. Find the force in the member QP of the frame shown below.

engineering-mechanics-questions-answers-simple-trusses-2-q12

a) 707.1N
b) 500N
c) 505N
d) 784N

View Answer

Answer: b [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

13. Which of the following is true?
a) If we are considering the clockwise direction to be positive then the rotation along the counter clockwise direction is negative
b) If we are considering the clockwise direction to be negative then the rotation along the counter clockwise direction is also negative as no such assumptions can be taken
c) If we are considering the clockwise direction to be positive then the rotation along the counter clockwise direction is also positive as no such assumptions can be taken
d) If we are considering the clockwise direction to be negative then the rotation along the counter clockwise direction is neither positive nor negative as we only pre assumed the clockwise direction

View Answer

Answer: a [Reason:] We can take such assumptions. We are free to do so. We just need to specify if clockwise is positive then the counter clockwise is to be negative. Also such assumption are very useful in 2D calculation of the moments caused by various forces on the body.

14. The moment is the cross product of which two vectors?
a) Force and Radius vectors
b) Radius and Force vectors
c) Force and Radius scalars
d) Radius and Force scalars

View Answer

Answer: b [Reason:] The cross product needs to take in the proper sequence. If not taken then the answer is just the opposite of the true answer. That’s why, the answer is not the Force and Radius vectors, but the Radius and Force vectors. Because the moment has its direction, as many of the cross products have, and thus precaution needs to be taken.

15. The ___________ forces do not cause the rotation.
a) Non-concurrent
b) Concurrent
c) Parallel
d) Non-Parallel

View Answer

Answer: b [Reason:] The concurrent forces are the which are somewhere touching the axis of rotation. If any of the force is touching that axis, that force is not considered, or is insufficient to cause a rotation. If a force is concurrent then the perpendicular distance of the force from the line of axis is zero, thus no rotation. As we know rotation is caused by moment.

Set 3

1. If the whole truss is in equilibrium then all the joints which are connected to that truss is in equilibrium. This is known as:
a) Method of joints
b) Section method
c) Scalar field method
d) Vector equilibrium method

View Answer

Answer: a [Reason:] If the whole truss is in equilibrium then all the joints which are connected to that truss is in equilibrium. This is known as method of joints. This is one of the methods to solve for the forces which are acting along the trusses.

2. Find the force in the member vertical at the right, joined by the hinge.

engineering-mechanics-questions-answers-method-joints-q2

a) 750N
b) 450N
c) 250N
d) 200N

View Answer

Answer: d [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

3. The free body diagram of which part of the section of the truss is made to make use of method of joints?
a) Joints
b) Truss
c) The whole structure
d) The combination of joint and the whole structure

View Answer

Answer: a [Reason:] The free body diagram of joints part of the section of the truss is made to make use of method of joints. Various equations of equilibrium are made to do the calculations. The net force acting on the vertical direction is made zero. Also horizontal direction forces are made to be zero.

4. For applying the method of joint at joints the forces need to coplanar.
a) False
b) True

View Answer

Answer: b [Reason:] The forces are coplanar that’s why they are there in the calculations in the method of joints. The forces are resolved in 2D. This makes the condition of the equilibrium fulfilled and hence the method of joints uses the forces in the same plane for its calculation.

5. For applying the method of joint at joints the forces need to be concurrent.
a) False
b) True

View Answer

Answer: b [Reason:] The forces are concurrent that’s why they are there in the calculations in the method of joints. The forces are resolved in 2D. This makes the condition of the equilibrium fulfilled by cancelling of various force members and hence the method of joints uses the concurrent forces for its calculation.

6. Find the force in the member RQ.

engineering-mechanics-questions-answers-method-joints-q6

a) 750N
b) 450N
c) 250N
d) 200N

View Answer

Answer: b [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

7. We use the method of joint to find the forces acting over the joints. In this we start from the joint having at least one known force and at the most two unknown forces.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: d [Reason:] This makes the calculations easy. Also for the solving of any equation one requires equal number of variables as that of equal number of equation. So to do the calculations easily the above mentioned conditions are followed.

8. We use the method of joint to find the net force acting over the entire structure.
a) True
b) False

View Answer

Answer: b [Reason:] We use this method for the simplification of the forces in the sections of the structure. Not the entire structure. This means that the statement given is wrong. It should be the joints not the whole structure.

9. Which of the following is correct?
a) To know the direction of the unknown force we take assumption of it
b) The direction of the unknown force is known to us already
c) The direction of the unknown can’t be determined
d) The direction of the unknown is of no use, it is not founded

View Answer

Answer: a [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly.

10. The magnitude of the unknown force can’t be known. But the direction can be founded out.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: a [Reason:] The first part is wrong. We can determine the magnitude of the unknown force. It can be done by using the equilibrium equations. That equating the forces zero, of the three different axis. Thus making the components of the unknown founded out.

11. Find the force in the member PQ.

engineering-mechanics-questions-answers-method-joints-q11

a) 750N
b) 450N
c) 250N
d) 200N

View Answer

Answer: c [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

12. What is after taking the assumption of the direction of the force, the direction comes opposite?
a) The assumption made was wrong and the question can’t be solved further
b) The assumptions are not to be taken
c) The direction is in the opposite sense, and hence the direction is known to us
d) The direction will be already given to us, no need of assuming

View Answer

Answer: c [Reason:] The direction is comes opposite, means that the assumption was wrong. But that doesn’t means that the question can’t be solved further. One needs to change the sign of the direction and the question is solved. Thus the calculations of the force direction.

13. The resultant of three equal vectors having mutual angles being 120 degree and being originated from a single point is zero.
a) True
b) False

View Answer

Answer: a [Reason:] As one can imagine three vectors coming out of a single point and are having a 120 degree angle with their adjacent ones, the resultant would be zero.

14. The magnitude of the resultant of the two vectors is always:
a) Greater than one of the vector’s magnitude
b) Smaller than one of the vector’s magnitude
c) Depends on the angle between them
d) Axis we choose to calculate the magnitude

View Answer

Answer: c [Reason:] Yes, the magnitude of the resultant of the two vectors always depends on the angle between them. It might be greater or smaller than one of the vector’s length. For perfectly saying, it does depends upon the angle between them.

15. Find the force in the member PR.

engineering-mechanics-questions-answers-method-joints-q15

a) 750N
b) 450N
c) 250N
d) 200N

View Answer

Answer: a [Reason:] The direction of the unknown is not known to us. To know the direction of the unknown force we take assumption of it. That is we assume that the particular direction might be the direction of the force and then we do the calculations accordingly. And then we apply the equilibrium equations to the joints.

Set 4

1. We use the method of joints when the members on which the force to be found are few in number.
a) True
b) False

View Answer

Answer: a [Reason:] For few members we use method of joints to find the unknown force. It defines as if the whole truss is in equilibrium then all the joints which are connected to that truss is in equilibrium. This is known as method of joints. But when the system becomes complex, method of section comes into the picture.

2. The method of section cuts the whole structure of trusses into section and then uses the cut out portion for the calculations.
a) True
b) False

View Answer

Answer: a [Reason:] The method of section cuts the whole structure of trusses into section and then uses the cut out portion for the calculations. In which the net force equals zero equation is used. The net moment is made to be zero, etc. All these conditions of equilibrium is applied.

3. The method of joints helps us to find out the unknown force in the trusses joint. And the method of section helps us to make the calculation of the direction of the zero members.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: c [Reason:] Method of joints defines as if the whole truss is in equilibrium then all the joints which are connected to that truss is in equilibrium. While the method of section cuts the whole structure of trusses into section and then uses the cut out portion for the calculations of the unknown forces. Thus both the methods are used for the same purpose.

4. Method of section cuts the whole structure of trusses into section and then uses the cut out portion for the calculations of the unknown forces. For this method, at most two forces must be collinear.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: c [Reason:] Method of section cuts the whole structure of trusses into section and then uses the cut out portion for the calculations of the unknown forces. For this method, we don’t require two forces to be collinear. But if the forces are collinear than the task of determining the unknown forces is very easy.

5. The determination of the truss’s support reaction is done first and then the section is isolated for the method of the section.
a) The first step is right but the second one is wrong
b) The first step is wrong and the second one is wrong too
c) The first step is right and the second one is right too
d) The first step is wrong but the second one is right

View Answer

Answer: c [Reason:] The determination of the force of the unknown element is done by the method of section. For this the section is isolated from the main structure and then calculation is done after. But before that the determination of the support reaction needs to be done.

6. Why the determination of the support reaction needs to be done before isolating the section?
a) This reduces the calculation and also the labour
b) This makes the isolated section more complicated
c) This results in reduction on the formulas used
d) This procedure is not done at all, it of no need

View Answer

Answer: a [Reason:] The determination of the force of the unknown element is done by the method of section. For this the section is isolated from the main structure and then calculation is done after. But before that the determination of the support reaction needs to be done.

7. The free diagram of the section of the truss is made for the section having the least number of the forces. This is done as to make the calculations easy.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: d [Reason:] The part of the calculation is made easier if the flow diagram of that section is made which is having the least number of forces. Thus for the sake of the calculation this is done. Or one can say that for getting the unknown force we use this method.

8. We have three method to solve for the unknown force in the trusses. They are method of section, method of joints and rotational vector method.
a) The first part of the statement is false and other part is true
b) The first part of the statement is false and other part is false too
c) The first part of the statement is true and other part is false
d) The first part of the statement is true and other part is true too

View Answer

Answer: b [Reason:] The main methods for the solving for the unknown force on the truss are method of section and the method of joints. The other method is just given for the sake of confusion. This means that only two main methods are to applied for solving the unknown force on truss.

9. The free body diagram of which part of the section of the truss is made to make use of method of sections?
a) Joints
b) Truss
c) The whole structure
d) Any section can be used

View Answer

Answer: d [Reason:] The free body diagram of any part of the section of the truss is made to make use of method of sections. Various equations of equilibrium are made to do the calculations. The net force acting on the vertical direction is made zero. Also horizontal direction forces are made to be zero.

10. Determine the force in members UT.

engineering-mechanics-questions-answers-method-sections-q10

a) 1980N
b) 800N
c) 2200N
d) 1100N

View Answer

Answer: b [Reason:] The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

11. Determine the force in members UR.

engineering-mechanics-questions-answers-method-sections-q11

a) 1980N
b) 800N
c) 2200N
d) 1100N

View Answer

Answer: a [Reason:] The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

12. Determine the force in members QR.

engineering-mechanics-questions-answers-method-sections-q12

a) 1980N
b) 800N
c) 2200N
d) 1100N

View Answer

Answer: c [Reason:] The summation of the forces needs to be zero. So does the summation of the moments need to zero. But talking about the angles, they not needed to zero. But the forces which are acting at particular angles, must needed to be equal to zero. The basic need of the forces to make the body in equilibrium.

13. The system of the collinear and the parallel force are simplified as:
a) The simplified collinear force system gives us a net force and the parallel force system gives us a simplified force, and then we add it vectorially
b) Such simplification is not possible
c) The simplification is usually done by not considering the directions of the both
d) The simplification is done by considering the rotations only

View Answer

Answer: a [Reason:] The simplification is easy. The simplified force system gives us a net force and the parallel force system gives us a simplified force, and then we add it vectorially. Thus the vector addition at the last can be easily done and thus both can be simplified.

14. The couple and the other two force systems can be easily simplified.
a) Statement is wrong
b) Statement is right
c) Statement is right if we remove ‘couple’ part
d) Statement is right if we remove ‘force’ part

View Answer

Answer: b [Reason:] Both of them are vector quantities. And both of them can be easily simplified. If taken in the vector form then the task is even easier. Thus it is not necessary for the force or the couple to be vector only, even if the magnitude is taken, the simplification is done in the 2D.

15. The resultant force is equal to the _______ of all the forces.
a) Sum
b) Product
c) Subtraction
d) Division

View Answer

Answer: a [Reason:] As the simplification means addition and the subtraction of the forces. This results in the simplification of the forces and thus gives us a single force. It is in a particular direction. But if one is considering the direction with the magnitude of the force, we can say that the resultant is the sum of all the forces.

Set 5

1. Couple is having a combination of two forces. They are different in magnitude.
a) True
b) False

View Answer

Answer: b [Reason:] The couple is a combination of two forces of same magnitude. They are acting in the same sense of rotation. That is they are acting in the opposite direction, but giving the body a rotation in the same direction. Whether it may be in clockwise direction or anti-clockwise.

2. Determine the couple moment acting on the beam shown.
engineering-mechanics-questions-answers-moment-couple-q2

a) 500Nm
b) 1500Nm
c) 740Nm
d) 50Nm

View Answer

Answer: c [Reason:] As we know that the moment is vector quantity, their summation requires vector math. The couple moment is also the same. That is they are also the vectors, and requires vector math. Thus the resultant couple moment is the vector sum of the various couples acting in the body.

3. The distance between the forces acting in the couple is ____________
a) Infinity
b) Zero
c) A finite distance
d) A circular loop

View Answer

Answer: c [Reason:] The distance between the forces acting in the couple is having a finite distance. Couple is the combination of two forces which are acting in the same sense of rotation. That is they are acting in the opposite direction to provide a same direction rotation.

4. The resultant force acting in the couple is _________
a) Zero
b) Infinite
c) Twice the magnitude of the single force
d) Half the magnitude of the single force

View Answer

Answer: a [Reason:] The resultant of the force acting on the couple is always zero. As the force are acting in the opposite directions. So if we add the forces algebraically then the sum is going to be zero. Or in other words they cancel each other.

5. A man is travelling in the car. He is driving the car. If he is taking a turn in the road. He is applying force to the steering wheel by holding the wheel with his both hands. The steering wheel is facing a moment of force.
a) True
b) False

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Answer: b [Reason:] The man is trying to rotate the wheel by applying the force. The force is being applied on the steering wheel. Which is rotating the wheel, but it is the moment of the couple. Because the man has holded the wheel with his both hands, hence it is not the moment of the force.

6. Which of the following is correct for the moment of couple M caused by two forces of same magnitude F and are separated by a distance of r?
a) M = rxF
b) M = r.F
c) M = -(rxF)
d) M = -(r.F)

View Answer

Answer: a [Reason:] The answer is M = rxF. The moment id the cross product of the distance and the forces. It is the direction as directed by the curling of the hand. The thumb representing the direction of the moment. And the motion of the finger, that is the rotation gives the direction of the rotation caused by the forces.

7. A couple moment is a _______ vector.
a) Gradient
b) Scalar
c) Del
d) Free

View Answer

Answer: d [Reason:] A couple moment is a free vector. It can be act anywhere between the forces. As the couple is formed by two forces acting in the opposite directions. These forces are separated by a distance r, say, then the moment caused by them can act anywhere in between these forces.

8. Determine the couple moment acting on the beam shown.

engineering-mechanics-questions-answers-moment-couple-q8

a) 20KNm
b) 21KNm
c) 22KNm
d) 19KNm

View Answer

Answer: a [Reason:] As we know that the moment is vector quantity, their summation requires vector math. The couple moment is also the same. That is they are also the vectors, and requires vector math. Thus the resultant couple moment is the vector sum of the various couples acting in the body.

9. Which of the following is correct?
a) The couple moment depends on the axis of rotation
b) The couple moment depends directly on the radius vector of forces
c) The couple moment depends only on the distance vector between the forces
d) The couple moment’s direction is given by the left hand rule

View Answer

Answer: c [Reason:] The couple moment depends only on the distance vector between the forces. The radius vector of the forces are not making the couple depended over it. But the distance vector is driven by subtracting the radius vectors of the forces. This means that, moment of the couple doesn’t directly depends on the radius vector of forces.

10. If the forces acting on the couple are in the same direction, that is they are not in the opposite direction as always they are, then?
a) The direction of the forces doesn’t determine the moment
b) The couple moment will be maximum
c) The couple is not possible
d) No change occurs

View Answer

Answer: c [Reason:] The forces are always in the opposite direction for the couple moment. But if they don’t act like the same, that is they change their directions and align themselves in the same direction then the couple is not possible.

11. Determine the couple moment acting on the pipe shown.

engineering-mechanics-questions-answers-moment-couple-q11

a) -130Nm
b) 130Nm
c) -120Nm
d) 120Nm

View Answer

Answer: a [Reason:] As we know that the moment is vector quantity, their summation requires vector math. The couple moment is also the same. That is they are also the vectors, and requires vector math. Thus the resultant couple moment is the vector sum of the various couples acting in the body.

12. The resultant couple moment is ____________ sum of various couples acting on the body.
a) Vector
b) Scalar
c) Scalar Triple
d) Dot

View Answer

Answer: a [Reason:] As we know that the moment is vector quantity, their summation requires vector math. The couple moment is also the same. That is they are also the vectors, and requires vector math. Thus the resultant couple moment is the vector sum of the various couples acting in the body.

13. Determine the couple moment acting on the triangular plane shown.

engineering-mechanics-questions-answers-moment-couple-q13

a) 1600Nm
b) 100Nm
c) 2600Nm
d) 600Nm

View Answer

Answer: c [Reason:] As we know that the moment is vector quantity, their summation requires vector math. The couple moment is also the same. That is they are also the vectors, and requires vector math. Thus the resultant couple moment is the vector sum of the various couples acting in the body.

14. If two forces magnitude F each are acting in the Cartesian coordinate and are acting at the points A(3,3) and B(-3,3). They are heading towards negative z direction and positive z direction respectively. The distance between them is given as r. The radius vectors of the force at A and B are Ra and Rb respectively. Then the moment is given as:
a) (Ra-Rb).F
b) (Rb-Ra).F
c) (Ra-Rb)xF
d) (Rb-Ra)xF

View Answer

Answer: d [Reason:] The moment of couple as we know is the cross product of the force and the distance between them. But in this case we are given the radius vectors of the forces. So when we apply the vector maths to find the distance between the forces we get that the distance r = Rb-Ra. Now that we have the distance, we cross it with the force.

15. Determine the couple moment acting on the pipe shown.

engineering-mechanics-questions-answers-moment-couple-q15

a) 108j + 144k Nm
b) -108j + 144k Nm
c) 108j – 144k Nm
d) -108j – 144k Nm

View Answer

Answer: a [Reason:] As we know that the moment is vector quantity, their summation requires vector math. The couple moment is also the same. That is they are also the vectors, and requires vector math. Thus the resultant couple moment is the vector sum of the various couples acting in the body.