Question

A ball is projected from a top of height, h = 45 m. It is projected horizontally with an initial speed of 30 m/s. Then, which of the following statement is incorrect?

• A. Ball will hit ground after 3 seconds
• B. Ball will hit ground with speed $30\sqrt{2}m/s$
• C. Ball will hit ground at angle ${45}^{\circ }$ with horizontal
• D. Change in momentum of ball is in horizontal direction

Answer 1

The correct option is D Change in momentum of ball is in horizontal direction

$h=\frac{1}{2}g{t}^2$ $45=5t^2$
$\overrightarrow{v}=\overrightarrow{u}+\overrightarrow{a}t$ $t^2=9=3$
$=30\hat{i}-30\hat{j}$
$\overrightarrow{\Delta p}$ = $-30\hat{j}$
So change in momentum is in downward direction.