Question

A ball is thrown vertically upward with a speed of $25.0m/s$. How long does the ball take to hit the ground after it reaches its highest point?

• A. $2.5s$
  
• B. $3s$
  
• C. $4s$
  
• D. $2s$
  

Answer 1

The correct option is A $2.5s$

When the ball reaches the highest point, its velocity will be zero. So final velocity is $v=0m/s$

Here, the time to reach highest point is equal to time to hit ground from highest point.

Consider upward motion, the acceleration of the ball is $a=-g=-9.8m/s^2$ (minus for motion opposite to gravity)

If $t$ be the required time.

Using $v=u+at$,

$0=25+(-9.8)t$

$⟹$ $t=2.5s$

Thus the ball hits the ground after $2.5$ seconds after reaching its highest point.