Question 357: Centre of Mass and Rotational Motion

Question

$N$ number of balls of mass $m \mathrm{~kg}$ moving along positive direction of $X$ - axis, strike a wall per second and return elastically. The velocity of each ball is $u \mathrm{~m} / \mathrm{s}$. The force exerted on the wall by the balls in newton, is

Accepted Answer

The change in momentum of one ball,
$$\Delta p=m u-(-m u)=2 m u$$
The force exerted on the wall by $N$ balls,
$$\begin{aligned}
F & =\frac{	ext { Change in momentum for } N 	ext { balls }}{	ext { Total time }(t)} \
& =\frac{2 m \mathrm{Nu}}{1} \quad (\because t=1s)\
& =2 m \mathrm{Nu}
\end{aligned}$$

Answer

0

Answer

$2 m N u$

Answer

$\frac{m N u}{2}$

Answer

$m N u$

Centre of Mass and Rotational Motion

N number of balls of mass m \mathrm{~kg} moving along positive direction of X - axis, strike a wall per second and return elastically. The velocity of each ball is u \mathrm{~m} / \mathrm{s}. The force exerted on the wall by the balls in newton, is

Choose the correct answer: