﻿ A bullet emerge from a barrel of length 1.2 m with a speed of 640 ms-1 . Assuming constant acceleration, the approximate time that it spends in the barrel after the gun is fired is | Motion in Straight Line

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# Motion in Straight Line

#### Multiple Choice Questions

111.

A rocket of mass 100 kg burns 0.1 kg of fuel per sec. If velocity of exhaust gas is 1 km/sec, then it lifts with an acceleration of

• 1000 ms-2

• 100 ms-2

• 10 ms-2

• 1 ms-2

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# 112.A bullet emerge from a barrel of length 1.2 m with a speed of 640 ms-1 . Assuming constant acceleration, the approximate time that it spends in the barrel after the gun is fired is4 ms 40 ms 400 μs 1 s

A.

4 ms

Given that, s = 1.2 m and v = 640 ms-1, a = ? ; u = 0 ; t = ?

We have the third equation of motion

2as = v2 − u2

2a × 1.2 = 640 × 640

or

and by first equation of motion

v = u + at

or          t = $\frac{\mathrm{v}}{\mathrm{a}}$ = $\frac{15}{4}$ × 10-3

= 3.75 × 10-3

s = 4 ms

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113.

The acceleration a (in ms-2 ) of a body, starting from rest varies with time t (in s) following the equation a = 3 t + 4. The velocity of the body at time t = 2 s will be

• 10 ms-1

• 18 ms-1

• 14 ms-1

• 26 ms-1

114.

Figure below shows the distance-time graph of the motion of a car. It follows from the graph that the car is

• at rest

• in uniform motion

• in non-uniform acceleration

• uniformly accelerated

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#### Short Answer Type

115.

A shell of mass m is at rest initially. It explodes into three fragments having masses in the ratio 2 : 2 : 1. The fragments having equal masses fly off along mutually perpendicular direction with speed v. What will be the speed of the third (lighter) fragment ?

#### Multiple Choice Questions

116.

If a person can throw a stone to maximum height of h metre vertically, then the maximum distance through which it can be thrown horizontally by the same person is

• $\frac{\mathrm{h}}{2}$

• h

• 2h

• 3h

117.

A box is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to

• t1/2

• t3/4

• t3/2

• t2

118.

A particle is moving with a constant speed v in a circle. What is the magnitude of average velocity after half  rotation ?

• 2v

• $2\frac{\mathrm{v}}{\mathrm{\pi }}$

• $\frac{\mathrm{v}}{2}$

• $\frac{\mathrm{v}}{2\mathrm{\pi }}$

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119.

A box of mass 2 kg is placed on the roof of a car. The box would remain stationary until the car attains a maximum acceleration. Coefficient of static friction between the box and the roof of the car is 0.2 and g = 10 ms-2. This maximum acceleration of the car, for the box to remain stationary, is

• 8 ms-2

• 6 ms-2

• 4 ms-2

• 2 ms-2

120.

A particle is travelling along a straight line OX. The distance x (in metre) of the particle from O at a time t is given by x = 37 + 27t − t3, where t is time in seconds. The distance of the particle from O when it comes to rest is

• 81 m

• 91 m

• 101 m

• 111 m

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