Question

A player throws a ball upwards with an initial speed of 30 m s^-1. How long does the ball take to return to the player’s hands? (Take g = 10 m s^-2)

• A. 3 s
• B. 6 s
• C. 9 s
• D. 12 s

Answer 1

Answer: (B)

6 s

Answer 2

Let t be times taken by the ball to reach the highest point.

As v = u + at

Here , u = $30 \mathrm {~ms} ^ { - 1 }$

V = 0 (At highest point velocity is zero)

$\mathrm { a } = - \mathrm { g } = - 10 \mathrm {~ms} ^ { - 1 }$

$\therefore$ 0 = 30 – 10t or t = 3s

$\therefore$ Time taken by the ball to return to player’s hand

=3s + 3s = 6s.