Question

A tennis ball is hit upwards at a speed of 15m/s.how high does the ball go ? How long does it take to hit the ground ?

Answer 1

Answer:

11.48 m

Explanation:

v^2 — u^2 = 2* a*s

v = 0

u = 15 m/s

a = -g

15*15 = 2 * 9.8 *s

s = 11.48 m

Answer 2

u = 15m/s

v = 0m/s

{ cause at some point it's velocity is gonna be 0 before falling)

g = -10 m/s²

{cause the ball is going upwards that is against gravity}

By equation,

v² = u²+2as

0 = 15²+2(-10)s

0 = 225 -20s

-225 = -20s

s = 11.25m

So, the ball goes 11.25m high.

v = u+at

0 = 15 -10t

-15 = -10t

t = 1.5 seconds

So, it takes 1.5 seconds to reach up.

Now,

s = ut+ ½at²

11.25 = 0 +½×10×t²

11.25 = 5t²

2.25 = t²

t = 1.5 seconds

Now, the ball takes 1.5 seconds to reach up, and 1.5 seconds to hit the ground from the upper position.

The time taken by the ball to hit the ground = 1.5+1.5 = 3 seconds

Cheers!