# Multiple choice question for engineering

## Set 1

1. The tooth profile most commonly used in gear drives for power transmission is

a) A cycloid

b) An involute

c) An ellipse

d) A parabola

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2. There are six gears A, B, C, D, E, F in a compound train. The numbers of teeth in the gears are 20, 60, 30, 80, 25 and 75 respectively. The ratio of the angular speeds of the driven (F) to the driver (A) of the drive is

a) 1/24

b) 1/8

c) 4/15

d) 12

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_{A}.T

_{C}.T

_{E}/T

_{B}.T

_{D}.T

_{F}= 20 x 30 x 25/60 x 80 x 75 = 1/24.

3. A fixed gear having 100 teeth meshes with another gear having 25 teeth, the centre lines of both the gears being joined by an arm so as to form an epicyclic gear train. The number of rotations made by the smaller gear for one rotation of the arm is

a) 3

b) 4

c) 5

d) 6

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_{100}/T

_{25}= 1 + 100/25 =5.

4. Speed reduction in a gear box is achieved using a worm and worm wheel. The worm wheel has 30 teeth and a pitch diameter of 210 mm. If the pressure angle of the worm is 20^{o}, what is the axial pitch of the worm?

a) 7 mm

b) 22 mm

c) 14 mm

d) 63 mm

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5. A speed reducer unit consists of a double-threaded worm of pitch = 11 mm and a worm wheel of pitch diameter = 84 mm. The ratio of the output torque to the input to rque is

a) 7·6

b) 12

c) 24

d) 42

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6. A pair of gears forms a rolling pair.

a) True

b) False

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7. Spiral bevel gears designed to be used with an offset in their shafts are called ‘hypoid gears’

a) True

b) False

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8. Gears with involute tooth profile transmit constant velocity ratios between shafts connected by them.

a) True

b) False

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9. In the case of spur gears, the mating teeth execute pure rolling motion with respect to each other from the commencement of engagement to its termination.

a) True

b) False

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10. A pair of helical gears has fewer teeth in contact as compared to an equivalent pair of spur gears.

a) True

b) False

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## Set 2

1. Which of the following screw thread is adopted for power transmission in either direction?

a) Acme threads

b) Square threads

c) Buttress threads

d) Multiple threads

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2. Multiple threads are used to secure

a) low efficiency

b) high efficiency

c) high load lifting capacity

d) high mechanical advantage

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3. Screws used for power transmission should have

a) low efficiency

b) high efficiency

c) very fine threads

d) strong teeth

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4. If α denotes the lead angle and φ, the angle of friction, then the efficiency of the screw is written as

a) tan(α − φ)/tanα

b) tanα/tan (α − φ)

c) tan(α + φ)/tanα

d) tanα/tan (α + φ)

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5. A screw jack has square threads and the lead angle of the thread is α. The screw jack will be self locking when the coefficient of friction (μ) is

a) μ > tan α

b) μ = sin α

c) μ = cot α

d) μ = cosec α

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6. To ensure self locking in a screw jack, it is essential that the helix angle is

a) larger than friction angle

b) smaller than friction angle

c) equal to friction angle

d) such as to give maximum efficiency in lifting

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7. A screw is said to be self locking screw, if its efficiency is

a) less than 50%

b) more than 50%

c) equal to 50%

d) none of the mentioned

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8. A screw is said to be over hauling screw, if its efficiency is

a) less than 50%

b) more than 50%

c) equal to 50%

d) none of the mentioned

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9. While designing a screw in a screw jack against buckling failure, the end conditions for the screw are taken as

a) both ends fixed

b) both ends hinged

c) one end fixed and other end hinged

d) one end fixed and other end free.

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10. The load cup of a screw jack is made separate from the head of the spindle to

a) enhance the load carrying capacity of the jack

b) reduce the effort needed for lifting the working load

c) reduce the value of frictional torque required to be countered for lifting the load

d) prevent the rotation of load being lifted

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## Set 3

1. The condition of correct gearing is

a) pitch line velocities of teeth be same

b) radius of curvature of two profiles be same

c) common normal to the pitch surface cuts the line of centres at a fixed point

d) none of the mentioned

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2. Law of gearing is satisfied if

a) two surfaces slide smoothly

b) common normal at the point of contact passes through the pitch point on the line joining the centres of rotation

c) number of teeth = P.C.D. / module

d) addendum is greater than dedendum

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3. Involute profile is preferred to cyloidal because

a) the profile is easy to cut

b) only one curve is required to cut

c) the rack has straight line profile and hence can be cut accurately

d) none of the mentioned

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4. The contact ratio for gears is

a) zero

b) less than one

c) greater than one

d) none of the mentioned

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5. The maximum length of arc of contact for two mating gears, in order to avoid interference, is

a) (r + R) sin φ

b) (r + R) cos φ

c) (r + R) tan φ

d) none of the mentioned

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6. When the addenda on pinion and wheel is such that the path of approach and path of recess are half of their maximum possible values, then the length of the path of contact is given by

a) (r + R) sin φ/2

b) (r + R) cos φ/2

c) (r + R) tan φ/2

d) (r + R) cot φ/2

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7. Interference can be avoided in involute gears with 20° pressure angle by

a) cutting involute correctly

b) using as small number of teeth as possible

c) using more than 20 teeth

d) using more than 8 teeth

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8. The ratio of face width to transverse pitch of a helical gear with α as the helix angle is normally

a) more than 1.15/tan α

b) more than 1.05/tan α

c) more than 1/tan α

d) none of the mentioned

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9. The maximum efficiency for spiral gears is

a) sin (θ + φ ) + 1/ cos (θ − φ ) + 1

b) cos (θ − φ) + 1/sin (θ + φ ) + 1

c) cos (θ + φ ) + 1/ cos (θ − φ ) + 1

d) cos (θ − φ) + 1/cos (θ + φ ) + 1

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_{max}= cos (θ + φ ) + 1/ cos (θ − φ ) + 1 where θ = Shaft angle, and φ = Friction angle.

10. For a speed ratio of 100, smallest gear box is obtained by using

a) a pair of spur gears

b) a pair of helical and a pair of spur gear compounded

c) a pair of bevel and a pair of spur gear compounded

d) a pair of helical and a pair of worm gear compounded

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## Set 4

1. A body is said to vibrate with simple harmonic motion if its acceleration is proportional to the distance from the mean position.

a) True

b) False

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2. The maximum displacement of a body, from its mean position is called amplitude.

a) True

b) False

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3. Frequency of vibrations is usually expressed in

a) number of cycles per hour

b) number of cycles per minute

c) number of cycles per second

d) none of the mentioned

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4. The amplitude of vibrations is always ______________ the radius of the circle.

a) equal to

b) less than

c) greater than

d) none of the mentioned

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5. The time taken by a particle for one complete oscillation is known as periodic time.

a) True

b) False

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6. The periodic time is given by

a) ω/2п

b) 2п/ω

c) ω x 2п

d) п/ω

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_{p}= 2п/ω seconds where ω = Angular velocity of the particle in rad/s.

7. When a body moves with simple harmonic motion, the product of its periodic time and frequency is equal to

a) zero

b) one

c) п/2

d) п

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8. The acceleration of the particle moving with simple harmonic motion is ____________ at the mean position.

a) zero

b) minimum

c) maximum

d) none of the mentioned

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9. The maximum velocity of a particle moving with simple harmonic motion is

a) ω

b) ωr

c) ω^{2}r

d) ω/r

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^{2}– x

^{2}The velocity is maximum at the mean position i.e. when x = 0.

Hence, v = ωr.

10. When a particle moves round the circumference of a circle of radius r with ω rad/s, then its maximum acceleration is ω^{2}r.

a) True

b) False

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^{2}r.

11. If a simple pendulum oscillates with an amplitude 50 mm and time period 2s, then its maximum velocity is

a) 0.1 m/s

b) 0.15 m/s

c) 0.8 m/s

d) 0.16 m/s

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_{max}= ωA where ‘ω’ is the angular frequency and ‘A’ is the amplitude. Therefore v

_{max}= (2π/T)A = (2π/2)×50×10-3 = 0.157 m/s.

12. A particle executes linear simple harmonic motion with an amplitude of 2 cm. When the particle is at 1 cm from the mean position, the magnitude of its velocity is equal to that of its acceleration. Then its time period in seconds is

a) 1/ 2π√3

b) 2π√3

c) 2π/√3

d) √3/2π

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13. Suppose you place a sphere of mass ‘m’ and radius ‘r’ inside a smooth, heavy hemispherical bowl of radius of 37r placed on a horizontal table. If the sphere is given a small displacement, what is its period of oscillation?

a) 2π√(m/37rg)

b) 2π√(m/rg)

c) 12π√(r/g)

d) 2π√(r/g)

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14. The instantaneous displacement of a simple harmonic oscillator is given by y = A cos(ωt + π/4). Its speed will be maximum at the time

a) 2π/ω

b) ω/2π

c) ω/π

d) π/4ω

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15. A particle of mass 5 g is executing simple harmonic motion with an amplitude 0.3 m and time period π/5 s. The maximum value of the force acting on the particle is

a) 5 N

b) 4 N

c) 0.5 N

d) 0.15 N

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## Set 5

1. Coriolis component of acceleration is a component of translatory acceleration.

a) True

b) False

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^{2}. Therefore translatory acceleration (a

_{t}= 2ωV).

2. If the relative motion between two links of a mechanism is pure sliding, then the relative instantaneous center for these two links does not exist.

a) True

b) False

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3. A slider sliding at 10 cm/s on a link which is rotating at 60 r.p.m. is subjected to Coriolis acceleration of magnitude

a) 40п^{2} cm/s^{2}

b) 0.4пcm/s^{2}

c) 40пcm/s^{2}

d) 4пcm/s^{2}

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^{2}

4. A body in motion will be subjected to coriolis acceleration when that body is

a) in plane rotation with variable velocity

b) in plane translation with variable velocity

c) in plane motion which is a resultant of plane translation and rotation

d) restrained to rotate while sliding over another body

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5. Mechanism used to produce a diagram to an enlarged or reduced sacle

a) hart’s mechanism

b) pantograph

c) grasshopper mechanism

d) peaucellier’s mechanism

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6. A straight line mechanism made up of turning pairs

a) hart’s mechanism

b) pantograph

c) grasshopper mechanism

d) none of the mentioned

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7. Approximate straight line motion consisting of one sliding pair

a) hart’s mechanism

b) pantograph

c) grasshopper mechanism

d) peaucellier’s mechanism

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8. Exact straight line motion mechanism

a) hart’s mechanism

b) pantograph

c) grasshopper mechanism

d) none of the mentioned

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9. The sense of Coriolis component 2ωV is the same as that of the relative velocity vector V rotated.

a) 45^{0} in the direction of rotation of the link containing the path

b) 45^{0} in the direction opposite to the rotation of the link containing the path

c) 90^{0} in the direction of rotation of the link containing the path

d) 180^{0} in the direction opposite to the rotation of the link containing the path

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^{0}in the direction of rotation of the link containing the path. The direction of coriolis component is along a line rotated 90

^{0}from the sliding velocity in a direction same as that of the angular velocity of the slotted lever.

10. What is the direction of the coriolis component of acceleration in a slotted lever-crank mechanism?

a) Along the sliding velocity vector

b) Along the direction of the crank

c) Along a line rotated 90^{0} from the sliding velocity vector in a direction opposite to the angular velocity of the slotted lever

d) Along a line rotated 90^{0} from the sliding velocity in a direction same as that of the angular velocity of the slotted lever.

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^{0}in the direction of rotation of the link containing the path. The direction of coriolis component is along a line rotated 90

^{0}from the sliding velocity in a direction same as that of the angular velocity of the slotted lever.