Question

A ball is thrown vertically up. If the ball reached at maximum height in $3s$. Assume air resistance is negligible. The maximum height of the ball is most nearly :

• A. $10m$
• B. $15m$
• C. $30m$
• D. $45m$
• E. $60m$

Answer 1

The correct option is D $45m$

Given : Time taken to reach the maximum height $t=3$ s $a=-g=-10m/s^2$

The initial velocity of the ball can be calculated by,

Using $v=u+at$

$\therefore$ $0=u-10\times 3$ $⟹u=30$ m/s

Using $S=ut+\frac{1}{2}a{t}^2$

$\therefore$ $S=30\times 3+\frac{1}{2}\times (-10)\times 3^2=45m$