Question

A ball is thrown vertically up with a velocity of $14.7$ $m/s$ from the top of a tower of height $49$ m. On its return, it misses the tower and finally strikes the ground. The time that elapsed from the instant the ball was thrown until it passes the edge of the tower is_______

• A. $1.5s$
• B. $3s$
• C. $6s$
• D. $0.5s$

Answer 1

The correct option is B $3s$

Let time for this $=t$
$\Rightarrow s=ut-\frac{1}{2}g{t}^2$

When Ball A returns to edge of tower, $s=0.$
$\Rightarrow 0=14.7t-\frac{1}{2}\times 9.8t^2$

Solving this quadratic equation we get:
$\Rightarrow t=0,3sec$
$\Rightarrow t=3sec$