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

• 4 ms

• 40 ms

• 400 μs

• 1 s

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

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

204.

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 ?

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

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

• t^1/2

• t^3/4

• t^3/2

• t²

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

• 2v

• $2\frac{\mathrm{v}}{\mathrm{\pi }}$

• $\frac{\mathrm{v}}{2}$

• $\frac{\mathrm{v}}{2\mathrm{\pi }}$

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

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

From the top of a tower, 80 m high from the ground, a stone is thrown in the horizontal direction with a velocity of 8 ms^-1 . The stone reaches the ground after a time 't' and falls at a distance of 'd' from the foot of the tower. Assuming g = 10 m/s², the time t and distance d are given respectively by

• 6 s, 64 m

• 6 s, 48 m

• 4 s, 32 m

• 4 s, 16 m