Question

A ball is dropped from a height of 90 m on a floor. At each collision with the floor. At each collision with the floor, the ball loses one tenth of its speed. plot the speed- time graph of its motion between t = 0 to t = 12s. 

Answer 1

Here, u₁ = 0, S₁ = 90 m,

a₁ = 9.8 ms^-2

As v₁² - u₁² = 2a₁.s_1.

v₁² = 0 +2 x 9.8 x 90

or, v₁ = √1764 ms^-1

Now, as we know, time of ascent = time of descent = 3.9s.

Total time elasped, before the upward motion of the ball 

= 4.2 +3.9 + 3.9 = 12.0 second.

The velocity with which the ball will hit the ground.

= u₃ = u₂ = 37.8 ms^-1.