From a lift moving upwards with a uniform acceleration a = 2ms-2, a man throws a ball vertically upwards …..

Q. From a lift moving upwards with a uniform acceleration a = 2ms-2, a man throws a ball vertically upwards with a velocity v = 12 ms-1 relative to the lift. The ball comes back to the man after a time t. Find the value of t in second (g=10ms-2).

(a) 4

(b) 2

(c)5

(d) 6

Ans: (b)

A ball is dropped vertically from a height d above the ground. It hits the ground and bounces up vertically to a height d/2…..

Q. A ball is dropped vertically from a height d above the ground. It hits the ground and bounces up vertically to a height d/2 . Neglecting subsequent motion and air resistance, its velocity v varies with height h above the ground as:

figure

Ans: (a)

Equation of motion of a body is dv/dt= -4v+8. Where v is the velocity in m/s and t is the time in second…..

Q. Equation of motion of a body is \displaystyle \frac{dv}{dt} = -4v + 8 . Where v is the velocity in m/s and t is the time in second. Initial velocity of the particle was zero. Then

(a) the initial rate of change of acceleration of the particle is 8 m/s³

(b) the terminal speed is 2 m/s

(c) Both (a) and (b) are correct

(d) Both (a) and (b) are wrong

Ans: (b)

A target is made of two plates, one of wood and the other of iron. The thickness of the wooden plate is 4cm and that of iron plate is 2cm…..

Q. A target is made of two plates, one of wood and the other of iron. The thickness of the wooden plate is 4cm and that of iron plate is 2cm. A bullet fired goes through the wood first and then penetrates 1cm into iron. A similar bullet fired with the same velocity from opposite direction goes through iron first and then penetrates 2cm into wood. If a1 and a2 be the retardations offered to the bullet by wood and iron plates respectively, then

(a) a1 = 2a2

(b) a2 = 2a1

(c) a1 = a2

(d) Data insufficient

Ans: (b)