Question

11. Evelyn rolled a tennis ball down the hallway.The ball had a negative acceleration of -0.4m/s2 until it came to a stop 8 seconds later.With what initial velocity did Evelyn roll theball?A. -20 m/sB. 20 m/sC. -3.2 m/sD. 3.2 m/s

Answer 1

Given data:

* The final velocity of the ball is 0m/s.

* The acceleration of the ball is,

`a=-0.4ms^(-2)`

* The time taken by the ball is 8 s.

Solution:

By the kinematics equation, the initial velocity of the ball in terms of the final velocity, acceleration, and the time taken is,

`v-u=at`

where v is the final velocity, u is the initial velocity, a is the acceleration and t is the time taken,

Substituting the known values,

`\begin{gathered} 0-u=-0.4*8 \\ -u=-3.2 \\ u=3.2\text{ m/s} \end{gathered}`

Thus, the initial velocity of the ball is 3.2 m/s.

Hence, option D is the correct answer.