how long will it take a ball to reach its highest point

Question

ball is thrown straight up in the air with initial speed of 7.0 m/s

Answer 1

The ball is thrown with initial velocity, u=7 m/s

The acceleration due to gravity on the ball is a=-g=-9.8 m/s^2 (acting downwards so -ve sign)

Since the ball is decelerating, its velocity is decreasing and becomes zero at highest point.

i.e at highest point v=0

Now using

v=u+at

we get

0=7-9.8t => t= 7/9.8 = 0.7 sec