# Practice Test: Question Set - 21

**1. On a ladder resisting on a smooth ground and leaning against a rough vertical wall, the force of friction acts**

- (A) Towards the
wall at its upper end

- (B) Away from
the wall at its upper end

- (C) Upwards at
its upper end

- (D) Downwards at
its upper end

**2. The velocity ratio of the differential wheel and axle is**

- (A)

*R*/

*r*-

_{1}*r*

_{2}- (B) 2

*R*/

*r*

_{1}- (C) 3

*R*/

*r*-

_{1}*r*

_{2}- (D) 2

*R*/

*r*+

_{1}*r*

_{2}**3. Joule is the unit of**

- (A) Power

- (B) Impulse

- (C) Work

- (D) Momentum

**4. Total no of instantaneous centers of a machine having ‘**

*n’*links, is- (A)

*n*/2

- (B)

*n*

- (C) (

*n*- 1)

- (D)

*n*(n - 1)/2

**5. For a body moving with simple harmonic motion, the number of cycles per second, is known as its**

- (A) Oscillation

- (B) Amplitude

- (C) Periodic
time

- (D) Frequency

**6. A ball is dropped from a height of 16 m on a horizontal floor. If it rebounds to a height of 9 m after striking the floor, the coefficient of restitution between ball and floor is**

- (A) 1/4

- (B) 2/3

- (C) 3/4

- (D) 4/3

**7. The motion of a bicycle wheel is**

- (A) Translatory

- (B) Rotary

- (C) Rotary
and translatory

- (D) Curvilinear

**8. For a simple pendulum, time period for a beat, is**

- (A)

*π*√

*(l*/

*g)*

- (B)

*π*√

*(*2

*l*/

*g)*

- (C)

*π*√

*(g*/2

*l)*

- (D)

*π*√

*(l*/2

*g)*

**9. A circular disc rotates at n rpm. The angular velocity of a circular ring of same mass and radius as the disc and to have the same angular momentum is**

- (A)

*n*rpm

- (B)

*n*/2 rpm

- (C)

*n*/4 rpm

- (D) 2

*n*rpm

**10. The rotational velocity of a satellite is increased by 450 m per second if its launch is done from equator**

- (A) Eastward

- (B) Northward

- (C) Westward

- (D) Southward

**11. The velocity of a body fallen from height ‘**

*h’*, on reaching the ground is given by- (A)

*v*= 2

*gh*

- (B)

*v*= 2

*gh*

^{2}

- (C)

*v*= √

*(*2

*gh)*

- (D)

*v*= 1/√

*(*2

*gh)*

**12. In SI units, the units of force and energy are respectively**

- (A) Newton and watt

- (B) Dyne and erg

- (C) Newton and joule

- (D) kg wt and joule

**13. The point about which combined motion of rotation and translation of a rigid body takes place, is known as**

- (A) Virtual centre

- (B) Instantaneous
centre

- (C) Instantaneous
axis

- (D) Point of
rotation

**14. For a given velocity of a projectile, the range is maximum when the angle of projection is**

- (A) 30°

- (B) 45°

- (C) 90°

- (D) 0°

**15. Time of flight of a projectile on a horizontal plane, is**

- (A) 2

*u sinα*/

*g*

- (B) 2

*u cosα*/

*g*

- (C) 2

*u tanα*/

*g*

- (D) 2

*u cotα*/

*g*

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