Question

How long will the ball take to reach its starting point? (in seconds)

• A. $1.5$
  
• B. $1.6$
  
• C. $2$
  
• D. $1$
  

Answer 1

The correct option is B $1.6$

Considering upward direction to be positive direction.
Initial velocity of ball $u=+8m/s$
Since the ball comes back to the initial position, the speed of the ball at that instant is equal to initial speed but in opposite direction.
So final velocity of ball $v=-8m/s$
Acceleration due to gravity $g=-10m/s^2$
Using $v=u+gt$
Or $-8=8-10t$
Or $10t=16$
$⟹t=1.6s$