Question

A ball of mass m moves with speed $v$ and it strikes normally with a wall and reflected back normally. If its time of contact with wall is $t$, then find force exerted by ball on the wall.

• A. $\frac{2mv}{t}$
• B. $\frac{mv}{t}$
• C. $mvt$
• D. $\frac{mv}{2t}$

Answer 1

Answer: (A)

$\frac{2mv}{t}$

Answer 2

Initial velocity of ball $=v$
When it strikes the wall normally and reflected back, then final velocity $=-v$
Change in velocity $=v-(-v)=2v$
Force exerted by the ball on the wall is given by
Newtons second law, i.e., $F= ma$
$=\frac{m\Delta v}{\Delta t}$
$=\frac{m(2v)}{t}$
$=\frac{2mv}{t}$