# Multiple choice question for engineering

## Set 1

1. The unit of linear acceleration is

a) kg-m

b) m/s

c) m/s^{2}

d) rad/s^{2}

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^{2}.

2. The angular velocity (in rad/s) of a body rotating at N r.p.m. is

a) π N/60

b) 2 π N/60

c) π N/120

d) π N/180

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3. The linear velocity of a body rotating at ω rad/s along a circular path of radius r is given by

a) ω.r

b) ω/r

c) ωs^{2}.r

d) ωs^{2}/r

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4. When a particle moves along a straight path, then the particle has

a) tangential acceleration only

b) centripetal acceleration only

c) both tangential and centripetal acceleration

d) none of the mentioned

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5. When a particle moves with a uniform velocity along a circular path, then the particle has

a) tangential acceleration only

b) centripetal acceleration only

c) both tangential and centripetal acceleration

d) none of the mentioned

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6. When the motion of a body is confined to only one plane, the motion is said to be

a) plane motion

b) rectilinear motion

c) curvilinear Motion

d) none of the mentioned

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7. _______________ is the simplest type of motion and is along a straight line path.

a) plane motion

b) rectilinear motion

c) curvilinear Motion

d) none of the mentioned

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8. _________________ is the motion along a curved path.

a) plane motion

b) rectilinear motion

c) curvilinear Motion

d) none of the mentioned

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9. Displacement of a body is a ___________ quantity.

a) scalar

b) vector

c) scalar and vector

d) none of the mentioned

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10. A train covers 60 miles between 2 p.m. and 4 p.m. How fast was it going at 3 p.m.?

a) 60 mph

b) 30 mph

c) 40 mph

d) 50 mph

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60 miles/ 2 hours = 30 mph

## Set 2

1. The force which acts along the radius of a circle and directed ____________ the centre of the circle is known as centripetal force.

a) away from

b) towards

c) at the

d) none of the mentioned

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2. The unit of mass moment of inertia in S.I. units is

a) m^{4}

b) kgf-m-s^{2}

c) kg-m^{2}

d) N-m

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^{2}.

3. Joule is a unit of

a) force

b) work

c) power

d) none of the mentioned

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4. The energy possessed by a body, for doing work by virtue of its position, is called

a) potential energy

b) kinetic energy

c) electrical energy

d) chemical energy

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5. When a body of mass moment of inertia I (about a given axis) is rotated about that axis with an angular velocity, then the kinetic energy of rotation is

a) 0.5 I.ω

b) I.ω

c) 0.5 I.ω^{2}

d) I.ω^{2}

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^{2}

When a body has both linear and angular motions e.g. in the locomotive driving wheels and wheels of a moving car, then the total kinetic energy of the body is equal to the sum of kinetic energies of translation and rotation.
∴ Total kinetic energy = 1/ 2mv^{2} +1/ 2I.ω^{2}

6. The wheels of a moving car possess

a) potential energy only

b) kinetic energy of translation only

c) kinetic energy of rotation only

d) kinetic energy of translation and rotation both.

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7. The bodies which rebound after impact are called

a) inelastic bodies

b) elastic bodies

c) solid bodies

d) none of the mentioned

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8. The coefficient of restitution for inelastic bodies is

a) zero

b) between zero and one

c) one

d) more than one

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9. Which of the following statement is correct ?

a) The kinetic energy of a body during impact remains constant.

b) The kinetic energy of a body before impact is equal to the kinetic energy of a body after impact.

c) The kinetic energy of a body before impact is less than the kinetic energy of a body after impact.

d) The kinetic energy of a body before impact is more than the kinetic energy of a body after impact.

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_{1}= 1/2 m

_{1}(u

_{1})

^{2}+ 1/2 m

_{2}(u

_{2})

^{2}

When the two bodies move with the same velocity v after impact, then Kinetic energy of the system after impact,

E_{2}= 1/2( m_{1} + m_{2}) v^{2}

∴ Loss of kinetic energy during impact,
E_{L} = E_{1} – E_{2}

10. A body of mass m moving with a constant velocity v strikes another body of same mass m moving with same velocity but in opposite direction. The common velocity of both the bodies after collision is

a) v

b) 2 v

c) 4 v

d) 8 v

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_{1}–

_{2}Here both the velocities are same. Therefore Common velocity = V – (-V) = V + V = 2V

## Set 3

1. The two parallel and coplaner shafts are connected by gears having teeth parallel to the axis of the shaft. This arrangement is known as

a) spur gearing

b) helical gearing

c) bevel gearing

d) spiral gearing

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2. The arrangement is called bevel gearing, when two __________ are connected by gears.

a) tension in the tight side of the belt

b) tension in the slack side of the belt

c) sum of the tensions on the tight side and slack side of the belt

d) average tension of the tight side and slack side of the belt

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3. When two non-intersecting and non-coplaner shafts are connected by gears,the arrangement is known as helical gearing.

a) True

b) False

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4. The gears are termed as medium velocity gears, if their peripheral velocity is

a) 1-3 m/s

b) 3-15 m/s

c) 15-30 m/s

d) 30-50 m/s

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5. An imaginary circle which by pure rolling action, gives the same motion as the actual gear, is called

a) addendum circle

b) dedendum circle

c) pitch circle

d) clearance circle

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6. The size of a gear is usually specified by

a) pressure angle

b) circular pitch

c) diametral pitch

d) pitch circle diameter

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7. The radial distance of a tooth from the pitch circle to the bottom of the tooth is called

a) dedendum

b) addendum

c) clearance

d) working depth

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8. The addendum is the radial distance of tooth from the pitch circle to the top of the tooth.

a) True

b) False

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9. The working depth of a gear is radical distance from the

a) pitch circle to the bottom of a tooth

b) pitch circle to the top of a tooth

c) top of a tooth to the bottom of a tooth

d) addendum circle to the clearance circle

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10. The radial distance from the top of a tooth to the bottom of a tooth in a meshing gear, is called

a) dedendum

b) addendum

c) clearance

d) working depth

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## Set 4

1. A multiple disc clutch has five plates having four pairs of active friction surfaces. If the intensity of pressure is not to exceed 0.127 N/mm^{2}, find the power transmitted at 500 r.p.m. The outer and inner radii of friction surfaces are 125 mm and 75 mm respectively. Assume uniform wear and take coefficient of friction = 0.3.

a) 17.8 kW

b) 18.8 kW

c) 19.8 kW

d) 20.8 kW

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_{1}+ n

_{2}= 5 ; n = 4 ; p = 0.127 N/mm

^{2}; N = 500 r.p.m. or ω = 2π × 500/60 = 52.4 rad/s ; r

_{1}= 125 mm ; r

_{2}= 75 mm ; μ = 0.3 Since the intensity of pressure is maximum at the inner radius r

_{2}, therefore p.r

_{2}= C or C = 0.127 × 75 = 9.525 N/mm We know that axial force required to engage the clutch, W = 2 π C (r

_{1}– r

_{2}) = 2 π × 9.525 (125 – 75) = 2990 N and mean radius of the friction surfaces, R = r

_{1}+ r

_{2}/2 = 125 + 75/2 = 100 mm = 0.1 m We know that torque transmitted, T = n.μ.W.R = 4 × 0.3 × 2990 × 0.1 = 358.8 N-m ∴ Power transmitted, P = T.ω = 358.8 × 52.4 = 18 800 W = 18.8 kW.

2. A single plate clutch, with both sides effective, has outer and inner diameters 300 mm and 200 mm respectively. The maximum intensity of pressure at any point in the contact surface is not to exceed 0.1 N/mm^{2}. If the coefficient of friction is 0.3, determine the power transmitted by a clutch at a speed 2500 r.p.m.

a) 61.693 kW

b) 71.693 kW

c) 81.693 kW

d) 91.693 kW

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_{1}= 300 mm or r

_{1}= 150 mm ; d

_{2}= 200 mm or r

_{2}= 100 mm ; p = 0.1 N/mm

^{2}; μ = 0.3 ; N = 2500 r.p.m. or ω = 2π × 2500/60 = 261.8 rad/s Since the intensity of pressure ( p) is maximum at the inner radius (r

_{2}), therefore for uniform wear, p.r

_{2}= C or C = 0.1 × 100 = 10 N/mm We know that the axial thrust, W = 2 π C (r

_{1}– r

_{2}) = 2 π × 10 (150 – 100) = 3142 N and mean radius of the friction surfaces for uniform wear, R = r

_{1}+ r

_{2}/2 = 150 + 100/2 = 125 mm = 0.125m We know that torque transmitted, T = n.μ.W.R = 2 × 0.3 × 3142 × 0.125 = 235.65 N-m …( n = 2,for both sides of plate effective) ∴ Power transmitted by a clutch, P = T.ω = 235.65 × 261.8 = 61 693 W = 61.693 kW.

3. A 60 mm diameter shaft running in a bearing carries a load of 2000 N. If the coefficient of friction between the shaft and bearing is 0.03, find the power transmitted when it runs at 1440 r.p.m.

a) 171.4 W

b) 271.4 W

c) 371.4 W

d) 471.4 W

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4. The force of friction is inversely proportional to the normal load between the surfaces.

a) True

b) False

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5. The force of friction is dependent of the area of the contact surface for a given normal load.

a) True

b) False

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6. The force of friction depends upon the material of which the contact surfaces are made.

a) True

b) False

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7. The force of friction is dependent of the velocity of sliding of one body relative to the other body.

a) True

b) False

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8. The force of friction is almost dependent of the load.

a) True

b) False

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9. The force of friction is dependent of the substances of the bearing surfaces.

a) True

b) False

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10. The force of friction is _____________ for different lubricants.

a) same

b) different

c) zero

d) none of the mentioned

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## Set 5

1. The force of friction always acts in a direction, ___________ to that in which the body tends to move.

a) same

b) opposite

c) both of the mentioned

d) none of the mentioned

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2. The magnitude of the force of friction is ____________ to the force, which tends the body to move.

a) equal

b) different

c) both of the mentioned

d) none of the mentioned

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3. The magnitude of the limiting friction (F ) bears a constant ratio to the normal reaction (R_{N}) between the two surfaces.

a) True

b) False

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_{N}) between the two surfaces. Mathematically F/RR

_{N}= constant.

4. The force of friction is _____________ of the area of contact, between the two surfaces.

a) dependent

b) independent

c) both of the mentioned

d) none of the mentioned

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5. The force of friction does not depends upon the roughness of the surfaces.

a) True

b) False

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6. The ratio of magnitude of the kinetic friction to the normal reaction between the two surfaces is_____________ than that in case of limiting friction.

a) greater

b) less

c) equal

d) none of the mentioned

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7. For moderate speeds, the force of friction

a) increases

b) decreases

c) remains constant

d) none of the mentioned

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8. A body of mass 400 g slides on a rough horizontal surface. If the frictional force is 3.0 N, find the angle made by the contact force on the body with the vertical.

a) 35^{0}

b) 36^{0}

c) 37^{0}

d) 38^{0}

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^{2}) = 4.0 N. The frictional force is f = 3.0 N. tan ϴ = f/N = 3/4 or, ϴ = tan

^{-1}(3/4) = 37

^{0}.

9. A body of mass 400 g slides on a rough horizontal surface. If the frictional force is 3.0 N, find the magnitude of the contact force.

a) 5 N

b) 10 N

c) 15 N

d) 20 N

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^{2}) = 4.0 N. The frictional force is f = 3.0 N. F = √N

^{2}= √4

^{2}+ 3

^{2}= 5 N.

10. A heavy box of mass 20 kg is pulled on a horizontal surface by applying a horizontal force. If the coefficient of kinetic friction between the box and the horizontal surface is 0.25, find the force of friction exerted by the horizontal surface on the box.

a) 29 N

b) 39 N

c) 49 N

d) 59 N

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^{2}) = 49 N. This force acts in the direction opposite to the pull.

11. A boy (30 kg) sitting on his horse whips it. The horse speeds up at an average acceleration of 2.0 m/s 2.If the boy does not slide back, what is the force of friction exerted by the horse on the boy ?

a) 20 N

b) 30 N

c) 40 N

d) 60 N

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_{s}

As the boy does not slide back, its acceleration a is equal to the acceleration of the horse. As friction is the only horizontal force, it must act along the acceleration and its magnitude is given by Newton’s second law
f_{s} = Ma = (30 kg) (2.0 m/s^{2}) = 60 N.

12. A boy (30 kg) sitting on his horse whips it. The horse speeds up at an average acceleration of 2.0 m/s 2.If the boy slides back during the acceleration, what can be said about the coefficient of static friction between the horse and the boy.

a) 0.10

b) 0.20

c) 0.30

d) 0.40

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_{s}= μ

_{s}= μ

_{s}Mg

μ_{s}(30 kg) (10m/s^{2}) = μ_{s} 300 N
where μ_{s} is the coefficient of static friction. Thus,
μ_{s}(300 N) <60 N
or, μ_{s} <60/300 = 0.20.

13. A wooden block is kept on a polished wooden plank and the inclination of the plank is gradually increased. It is found that the block starts slipping when the plank makes an angle of 18° with the horizontal. However, once started the block can continue with uniform speed if the inclination is reduced to 15°. Find the coefficient of static friction between the block and the plank.

a) tan 18^{0}

b) tan 15^{0}

c) tan 33^{0}

d) tan 3^{0}

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_{s}= tan 18

^{0}.

14. A wooden block is kept on a polished wooden plank and the inclination of the plank is gradually increased. It is found that the block starts slipping when the plank makes an angle of 18° with the horizontal. However, once started the block can continue with uniform speed if the inclination is reduced to 15°. Find the coefficient of kinetic friction between the block and the plank.

a) tan 18^{0}

b) tan 15^{0}

c) tan 33^{0}

d) tan 3^{0}

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_{k}= tan 15

^{0}.