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Multiple choice question for engineering

Set 1

1. A body is consisted of __________ number of particles.
a) Infinite
b) Finite
c) Hundreds
d) Thousands

View Answer

Answer: a [Reason:] The various bodies are composed of infinite number of particles. They are very small in size. They cant be seen by our naked eyes. Thus the number of particles is not thousands nor hundreds. But it is uncountable.

2. A body’s all small particles have a small weight which is being applied by them to the body, which adds up to the total weight of the body.
a) True
b) False

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

3. The all small weights that are being applied by all the infinite particles of the body act __________ to each other.
a) Parallel
b) Perpendicular
c) Collinear
d) Divergent

View Answer

Answer: a [Reason:] All the small weights that are being applied by all the particles are being applied by them parallel to themselves. Thus the parallel is the right answer. Thus the total sum of all these small weights add up to the total weight of the body.

4. The total of all the weights of small particles adds up to give the total body weight. This weight is the force vector which is being passed by ________
a) Axis of rotation
b) Axis of rolling
c) Centre of Gravity
d) Centre of mass

View Answer

Answer: c [Reason:] The total body weight always passes through the centre of gravity. All the forces are parallel is the right answer. Thus the total sum of all these small weights add up to the total weight of the body. Which passes through the centre of gravity.

5. The centre of gravity is the ratio of ________ to _________
a) The product of centroid and weight to the total weight
b) The addition of centroid and weight to the total weight
c) The subtraction of centroid and weight to the total weight
d) The product of centroid and weight to the total mass

View Answer

Answer: a [Reason:] The product of the centroid of the section to its weight to the total weight of the body is the centre of gravity. Thus the answer. The ratio is generally used to locate the coordinate of the centroid or the centre of gravity.

6. The x axis coordinate and the y axis coordinate of the centre of gravity are having different types of calculations to calculate them.
a) True
b) False

View Answer

Answer: b [Reason:] The calculation is general to all the axis of coordinate system. This means that the calculations are generalised for all the axis. And it is the product of the centroid of the section to its mass to the total weight of the body is the centre of gravity.

7. The centre of mass is the ratio of ________ to _________
a) The product of centroid and mass to the total weight
b) The addition of centroid and weight to the total weight
c) The subtraction of centroid and weight to the total weight
d) The product of centroid and mass to the total mass

View Answer

Answer: d [Reason:] The product of the centroid of the section to its mass to the total mass of the body is the centre of mass. Thus the answer. The ratio is generally used to locate the coordinate of the centroid or the centre of mass.

8. The centre of volume is the ratio of ________ to _________
a) The product of centroid and mass to the total weight
b) The addition of centroid and weight to the total weight
c) The subtraction of centroid and volume to the total weight
d) The product of centroid and volume to the total volume

View Answer

Answer: d [Reason:] The product of the centroid of the section to its volume to the total volume of the body is the centre of volume. Thus the answer. The ratio is generally used to locate the coordinate of the centroid or the centre of volume.

9. Determine the y coordinate of centroid of the line in the shape of parabola as shown.

engineering-mechanics-questions-answers-centre-gravity-q9

a) 0.514m
b) 1.410m
c) 2.410m
d) 0.10m

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

10. Volume is best given by ___________
a) Product of mass and density
b) Ratio of mass to density
c) Addition of mass and density
d) Subtraction of mass and density

View Answer

Answer: b [Reason:] The density is the ration of the mass to the volume of the body. Thus arranging them and the volume is said to be as ratio of mass to density. This equation is generally used in the calculations of the centroid of the body or the centre of gravity.

11. We use sometimes the measures to know the direction of moment. It is done by right handed coordinate system. Which is right about it(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.

12. If A is any vector with Ai + Bj + Ck then what is the y-axis component of the vector if we are using the vector math to calculate the centre of gravity?
a) B units
b) A units
c) C units
d) Square root of sum of squares of the three, i.e. A, B and C

View Answer

Answer: a [Reason:] As the given vector is shown in the Cartesian system, the number with “j” is the Y-axis component of the given vector. With the numbers with “i” representing components of x-axis and “k” representing the z axis respectively.

13. If the force vector F acting along the centre of gravity is having its x-axis component being equal to Z N, y-axis component be X N and z-axis component be Y N then vector F is best represented by?
a) Xi + Yj + Zk
b) Yi + Xj + Zk
c) Zi + Yj + Xk
d) Zi + Xj + Yk

View Answer

Answer: d [Reason:] It is given that x, y and z-axis components are Z, X and Y respectively. Thus, just by placing the right coordinates we get option d to be correct. Here just the interchange of the axis’s representor with their respective axis is creating confusion. Which must be figured out.

14. Which statement is right for force acting by the small particles of the body having it’s vector form as = Ai + Bj + Ck?
a) In rectangular components representation of any vector we have vector F = Ai + Bj + Ck
b) In rectangular components representation of any vector we have vector F = Ax + By + Cz
c) In rectangular components representation of any vector we have vector F = Fx + Fy + Fz
d) In rectangular components representation of any vector we have vector F = Fi + Fj + Fk

View Answer

Answer: c [Reason:] As given the vector is F = Ai + Bj + Ck, this implies that the x ,y and z-axis components of this vector is A, B and C respectively. But, in rectangular components representation of any vector, the vector is written as F = Fx + Fy + Fz.

15. Determine the x coordinate of centroid of the line in the shape of parabola as shown.

engineering-mechanics-questions-answers-centre-gravity-q15

a) 0.410m
b) 1.410m
c) 2.410m
d) 0.10m

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

Set 2

1. The centre of mass is the ratio of ________ to _________
a) The product of centroid and mass to the total weight
b) The addition of centroid and weight to the total weight
c) The subtraction of centroid and weight to the total weight
d) The product of centroid and mass to the total mass

View Answer

Answer: d [Reason:] The product of the centroid of the section to its mass to the total mass of the body is the centre of mass. Thus the answer. The ratio is generally used to locate the coordinate of the centroid or the centre of mass.

2. Mass is best given by _______
a) Product of volume and density
b) Ratio of mass to density
c) Addition of mass and density
d) Subtraction of mass and density

View Answer

Answer: b [Reason:] The density is the ration of the mass to the volume of the body. Thus arranging them and the volume is said to be as ratio of mass to density. This equation is generally used in the calculations of the centroid of the body or the centre of mass.

3. We use sometimes the measures to know the direction of moment in the calculations of the centre of mass. It is done by right handed coordinate system. Which is right about it(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.

4. The total of all the masses of small particles adds up to give the total body mass. This mass lies along with gravity gives a force vector which is being passed by ________
a) Axis of rotation
b) Axis of rolling
c) Centre of Gravity
d) Centre of mass

View Answer

Answer: c [Reason:] The total body mass along with the product of gravity always passes through the centre of gravity. All the forces are parallel is the right answer. Thus the total sum of all these small weights add up to the total weight of the body. Which passes through the centre of gravity.

5. The all small masses that are being applied by all the infinite particles of the body act __________ to each other.
a) Parallel
b) Perpendicular
c) Collinear
d) Divergent

View Answer

Answer: a [Reason:] All the small masses that are being applied by all the particles are being applied by them parallel to themselves. Thus the parallel is the right answer. Thus the total sum of all these small weights add up to the total weight of the body.

6. A body’s all small particles have a small mass which is being applied by them to the body, which adds up to the total mass of the body.
a) True
b) False

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small masses that are been applied by all the particles. The smaller the particle the smaller the mass it applies. Thus the total mass of the body is the summation of all the infinite number of small masses applied to the body.

7. What is not the condition for the equilibrium in calculations involved in the determination of the centre of mass?
a) ∑Fx=0
b) ∑Fy=0
c) ∑Fz=0
d) ∑F≠0

View Answer

Answer: d [Reason:] For the equilibrium in the three dimensional system of axis we have all the conditions true as, ∑Fx=0, ∑Fy=0 and ∑Fz=0. Also we have the summation of the forces equal to zero. Which is not a non-zero value.

8. We first make equilibrium equations of the body by considering all the three dimensional forces and then the free body diagram is made and then equations are made to be applied so as to calculate the centre of mass.
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:] We first make the free body diagram and then we make the equilibrium equations to satisfy the given conditions. This helps us to solve the question easily. As this reduces the part of imagination and increases accuracy too.

9. Determine the y coordinate of centroid of the wire in the shape of circle as shown.

engineering-mechanics-questions-answers-centre-mass-q9

a) 2R/π
b) 2/π
c) 2R/3
d) 2R/5

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

10. If solving the question in 3D calculations is difficult, then use the 2D system and then equate the ratio of the product of the centroid of the section to its mass to the total mass of the body to the centre of mass.
a) True
b) False

View Answer

Answer: a [Reason:] The answer is obviously yes. If we are having any difficulty in making the vector components, then we can go in 2D. As if the particle is in equilibrium, the net force will be zero. No matter where you see first. Net force is zero.

11. One of the use of the centre of mass or centroid is as in the simplification of the loading system 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 simplification of the loading system 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.

12. If the non-Uniform loading is of the type of parabola then?
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.

13. If any external force also is applied on the distributed loading 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, 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. The body is sometimes acted by two or three force members. 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.

15. Determine the x coordinate of centroid of the wire in the shape of circle as shown.

engineering-mechanics-questions-answers-centre-mass-q15

a) 2R/π
b) 2/π
c) 2R/3
d) 2R/5

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

Set 3

1. Density is best given by _______
a) Product of volume and density
b) Ratio of mass to Volume
c) Addition of mass and density
d) Subtraction of mass and density

View Answer

Answer: b [Reason:] The density is the ratio of the mass to the volume of the body. Thus arranging them and the volume is said to be as ratio of mass to density. This equation is generally used in the calculations of the centroid of the body.

2. If solving the question in 3D calculations is difficult, then use the 2D system and then equate the ratio of the product of the centroid of the section to its mass to the total mass of the body to the centroid.
a) True
b) False

View Answer

Answer: b [Reason:] The answer is obviously no. Still if we are having any difficulty in making the vector components, then we can go in 2D. As if the particle is in equilibrium, the net force will be zero. No matter where you see first. Net force is zero. But the statement here is not correct about the centroid.

3. One of the use of the centroid is as in the simplification of the loading system 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 simplification of the loading system 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.

4. The use of centroid comes in picture as if the non-Uniform loading is of the type of parabola then what will be the best suited answer among the following?
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.

5. If any external force also is applied on the distributed loading 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, 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.

6. The x axis coordinate and the y axis coordinate of the centroid are having different types of calculations to calculate them.
a) True
b) False

View Answer

Answer: b [Reason:] The calculation is general to all the axis of coordinate system. This means that the calculations are generalised for all the axis. All the axis are given same priority. Thus no change in calculations.

7. The centre of ____________ is the ratio of the product of centroid and volume to the total volume.
a) Centroid axis
b) Density
c) Mass
d) Volume

View Answer

Answer: d [Reason:] The product of the centroid of the section to its volume to the total volume of the body is the centre of volume. Thus the answer. The ratio is generally used to locate the coordinate of the centroid or the centre of volume.

8. If the force vector F acting along the centroid is having its x-axis component being equal to Z N, y-axis component be X N and z-axis component be Y N then vector F is best represented by?
a) Xi + Yj + Zk
b) Yi + Xj + Zk
c) Zi + Yj + Xk
d) Zi + Xj + Yk

View Answer

Answer: d [Reason:] It is given that x, y and z-axis components are Z, X and Y respectively. Thus, just by placing the right coordinates we get option d to be correct. Here just the interchange of the axis’s representor with their respective axis is creating confusion. Which must be figured out.

9. Centroid of a body does depends upon the small weights of tiny particles. Which statement is right for force acting by the small particles of the body having it’s vector form as = Ai + Bj + Ck?
a) In rectangular components representation of any vector we have vector F = Ai + Bj + Ck
b) In rectangular components representation of any vector we have vector F = Ax + By + Cz
c) In rectangular components representation of any vector we have vector F = Fx + Fy + Fz
d) In rectangular components representation of any vector we have vector F = Fi + Fj + Fk

View Answer

Answer: c [Reason:] As given the vector is F = Ai + Bj + Ck, this implies that the x ,y and z-axis components of this vector is A, B and C respectively. But, in rectangular components representation of any vector, the vector is written as F = Fx + Fy + Fz.

10. Determine the y coordinate of centroid of the area in the shape of circle as shown.

engineering-mechanics-questions-answers-centroid-body-q10

a) 4R/π
b) 2/π
c) 2R/3
d) 2R/5

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

11. Centroid determination involves the calculations of various forces. In that forces are having various properties. That is force is developed by a support that not allows the ________ of its attached member.
a) Translation
b) Rotation
c) Addition
d) Subtraction

View Answer

Answer: a [Reason:] The force developed by a support doesn’t allow the translation of its attached member. This is the basic condition for the equilibrium of the forces in any dimension. This rule is applied when the support reactions are taken into the account for the equilibrium of the body.

12. What is not the condition for the equilibrium for the calculations used for the determination of the centroid in three dimensional system of axis?
a) ∑Fx=0
b) ∑Fy=0
c) ∑Fz=0
d) ∑F≠0

View Answer

Answer: d [Reason:] For the equilibrium in the three dimensional system of axis we have all the conditions true as, ∑Fx=0, ∑Fy=0 and ∑Fz=0. Also we have the summation of the forces equal to zero. Which is not a non-zero value.

13. The supports in the 3D are having more than three reaction forces. Because they are having three axis on which the components of the forces need to be zero.
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:] As 3D is defined as the three axis system, we have to consider the equilibrium in all the three axis. This will make the equilibrium go on all the axis of the 3D space. And hence will cancel all the forces. These are the points to be kept in considerence while determining the centroid.

14. If any body is tied to three or more ropes, and then is allowed to achieve its equilibrium. Then the equilibrium achieved is achieved w.r.t what?
a) The three axis of the body
b) The ground
c) The ropes direction
d) The weight direction

View Answer

Answer: b [Reason:] Yes, the equilibrium is being achieved w.r.t the ground. Like the motion w.r.t ground need be zero. That is the relative velocity of the object or the body must be zero w.r.t the ground. This means motion is in equilibrium. This equilibrium is also defined by the centroid axis.

15. Determine the x coordinate of centroid of the area in the shape of circle as shown.

engineering-mechanics-questions-answers-centroid-body-q15

a) 4R/π
b) 2/π
c) 2R/3
d) 2R/5

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.

Set 4

1. ____________ is the phenomena that resist the movement of the two surfaces in contact.
a) Friction
b) Motion
c) Circular movement
d) Rotation

View Answer

Answer: a [Reason:] The friction is the phenomena that defines that there is a resistance which is present there between the two surfaces. The two surfaces are in contact and the friction applies at that surface only, resisting the motion of the surface.

2. The frictional force always acts ____________ to the surface of the application of the friction.
a) Tangential
b) Perpendicular
c) Parallel
d) Normal

View Answer

Answer: a [Reason:] The friction is the phenomena that defines that there is a resistance which is present there between the two surfaces. This friction is applied tangentially to the surfaces in contact. Thus the main thing is that the forces on both of the surfaces act tangential to each other.

3. Dry friction is also called _____________
a) Column Friction
b) Coulomb Friction
c) Dry column friction
d) Surface friction

View Answer

Answer: b [Reason:] The dry friction is acted upon the surfaces. And they are tangential to each other. As we know the friction is the phenomena that defines that there is a resistance which is present there between the two surfaces. The dry friction is also termed as the Coulomb friction as it was given by C.A. Coulomb.

4. Who gave the concept of Dry friction?
a) C.A. Coulomb
b) GA. Coulomb
c) C.P Coulomb
d) Albert Einstein

View Answer

Answer: a [Reason:] The dry friction is also termed as the Coulomb friction as it was given by C.A. Coulomb. And they are tangential to each other. As we know the friction is the phenomena that defines that there is a resistance which is present there between the two surfaces.

5. At what conditions the dry friction occurs between the surfaces in contact?
a) When there is no lubricating fluid
b) When there is no friction fluid
c) When there is no adhesive fluid
d) When there is no cohesive fluid

View Answer

Answer: a [Reason:] When there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. Thus as the name suggests, dry friction. When there is no liquid present over there the surfaces are going to be said dry only. Thus the term dry friction.

6. The phenomena of horizontal pull and push explains what?
a) Theory of friction
b) Theory of relativity
c) Theory of action
d) Theory of forces

View Answer

Answer: a [Reason:] As we know that when there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. This is the phenomena that defines that there is a resistance which is present there between the two surfaces. Thus the pull and push phenomena explains the theory of friction.

7. Theory of friction is explained over a block of weight W. Which of the following is the property of the surface on which block is present?
a) Non-rigid
b) Coloured red
c) Having density in negative
d) The motion of that block is always horizontal

View Answer

Answer: a [Reason:] The block used to explain the theory of friction is a used in a deformable surface. As we know that the theory of friction says that when there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. Thus to show the same experiments are done over a non-rigid/deformable surface.

8. The block used to explain the theory of friction is kept over non-deformable surface.
a) True
b) False

View Answer

Answer: b [Reason:] The block used to explain the theory of friction is a used in a deformable surface. As we know that the theory of friction says that when there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. Thus to show the same experiments are done over a non-rigid/deformable surface.

9. In the explanation of the theory of friction, the block used have an assumption. That is the upper portion of the block is considered to be rigid.
a) True
b) False

View Answer

Answer: b [Reason:] The block used to explain the theory of friction is placed on a deformable surface. As we know that the theory of friction says that when there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. Thus to show the same, experiments are done over a non-rigid/deformable surface which is having a rigid shape.

10. The free body diagram used to explain the theory of dry friction is having ___________ distribution of both the normal forces and frictional surface.
a) Uneven
b) Even
c) Uniform
d) Equal

View Answer

Answer: a [Reason:] As we know that when there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. This is the phenomena that defines that there is a resistance which is present there between the two surfaces. Thus the pull and push phenomena explains the theory of friction. Thus the free body diagrams are having uneven distribution of the forces.

11. For equilibrium the normal forces acts in which direction in the free body diagrams?
a) Vertically Upward
b) Vertically Downward
c) Horizontally Right
d) Horizontally Left

View Answer

Answer: a [Reason:] As the loads are being acting in the downward direction. Thus to make the forces balance, the normal forces act in the vertically upward direction. As we know that when there is no lubricating fluid present between the surfaces in contact, the dry friction occurs. This friction magnitude is taken out from these normal forces.

12. What is not the condition for the equilibrium in free body diagram for calculation of the normal forces?
a) ∑Fx=0
b) ∑Fy=0
c) ∑Fz=0
d) ∑F≠0

View Answer

Answer: d [Reason:] For the equilibrium in the three dimensional system of axis we have all the conditions true as, ∑Fx=0, ∑Fy=0 and ∑Fz=0. Also we have the summation of the forces equal to zero. Which is not a non-zero value.

13. We first make equilibrium equations of the body by considering all the three dimensional forces acting on the section chosen and then the free body diagram is made and solved.
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:] We first make the free body diagram and then we make the equilibrium equations to satisfy the given conditions. This helps us to solve the question easily. As this reduces the part of imagination and increases accuracy too.

14. Calculate the product of normal force and the coefficient of friction between the body and the surface.

engineering-mechanics-questions-answers-characteristics-dry-friction-1-q14

a) 183N
b) 116N
c) 100N
d) 180N

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Answer: a [Reason:] The net forces acting on the body is shown by the help of the resultant forces. There are two types, first the frictional and the second is the normal. This is because the resultant forces have the sum of all the forces which are acting on the direction which is same.

15. Determine the distance between the points of action of the forces, that is the normal force and the self-weight force in the given figure.

engineering-mechanics-questions-answers-characteristics-dry-friction-1-q15

a) 9.08mm
b) 9.08cm
c) 9.08m
d) 9.8mm

View Answer

Answer: a [Reason:] The net forces acting on the body is shown by the help of the resultant forces. There are two types, first the frictional and the second is the normal. This is because the resultant forces have the sum of all the forces which are acting on the direction which is same.

Set 5

1. A ______________ body consists of a series of connected “simpler” shaped bodies.
a) Composite
b) Non-composite
c) Digital
d) Binary

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Answer: a [Reason:] A composite body consists of a series of connected simpler shaped bodies. That is the body is having two material as it’s constitutes. The main thing is that the single material is having the properties of two different materials.

2. Composite materials are of no use for the chemical engineers.
a) False
b) True

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Answer: a [Reason:] The composite materials are of much importance to the chemical engineer. This means that the composite materials are variedly used in the chemical industries. It can be used in the bridges made for the pipelines, etc.

3. The composite materials are lighter than their constituent material.
a) False
b) True

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Answer: b [Reason:] Yes the composite materials are lighter than the constituent material. This means that the density of the former is lighter than the latter. Thus imparting many qualities to the materials. Thus the material can be used variedly.

4. Composite materials can be of __________ shapes.
a) Any
b) Circular only
c) Rectangular only
d) Oval only

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Answer: a [Reason:] The composite materials can be of any shape. This means that the shape of the material can be varied. Thus any shape can be imparted to the composite materials and then be used in the industries variedly.

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

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Answer: c [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 properties of the body can be altered. Thus both are very important things to be known about the composite bodies.

6. The centre of mass for the composite body is the ratio of ________ to _________
a) The product of centroid and mass to the total weight
b) The addition of centroid and weight to the total weight
c) The subtraction of centroid and weight to the total weight
d) The product of centroid and mass to the total mass

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Answer: d [Reason:] The product of the centroid of the section to its mass to the total mass of the body is the centre of mass. Thus the answer. The ratio is generally used to locate the coordinate of the centroid or the centre of mass.

7. The total of all the masses of small particles adds up to give the total body mass of the composite body. This mass lies along with gravity gives a force vector which is being passed by ________
a) Axis of rotation
b) Axis of rolling
c) Centre of Gravity
d) Centre of mass

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Answer: c [Reason:] The total body mass along with the product of gravity always passes through the centre of gravity. All the forces are parallel is the right answer. Thus the total sum of all these small weights add up to the total weight of the body. Which passes through the centre of gravity.

8. One of the use of the centre of mass or centroid of the composite bodies is as in the simplification of the loading system the net force acts at the ___________ of the loading body.
a) Centroid
b) The centre axis
c) The corner
d) The base

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Answer: a [Reason:] In the simplification of the loading system the net force acts at the centroid of the composite body. That is if the loading system is in the form of the triangle then 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.

9. If any external force also is applied on the distributed loading 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

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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.

10. Two of the things of the composite materials are to be known so that their properties 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

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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 properties of the body can be altered. Thus both are very important things to be known about the composite bodies.

11. A composite body is consisted of __________ number of particles.
a) Infinite
b) Finite
c) Hundreds
d) Thousands

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Answer: a [Reason:] The various bodies are composed of infinite number of particles. They are very small in size. They can’t be seen by our naked eyes. Thus the number of particles is not thousands nor hundreds. But it is uncountable.

12. We use sometimes the measures to know the direction of moment. 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

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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.

13. What is not the condition for the equilibrium in three dimensional system of axis for the composite bodies?
a) ∑Fx=0
b) ∑Fy=0
c) ∑Fz=0
d) ∑F≠0

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Answer: d [Reason:] For the equilibrium in the three dimensional system of axis we have all the conditions true as, ∑Fx=0, ∑Fy=0 and ∑Fz=0. Also we have the summation of the forces equal to zero. Which is not a non-zero value.

14. Determine the x coordinate of centroid of the shape shown.

engineering-mechanics-questions-answers-composite-bodies-q15

a) 0.410m
b) 1.410m
c) 2.410m
d) 0.10m

View Answer

Answer: a [Reason:] The weight of the body is the sum of the all the small weights that are been applied by all the particles. The smaller the particle the smaller the weight it applies. Thus the total weight of the body is the summation of all the infinite number of small weights applied to the body.