Tag: force exerted by collision

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Multiple choice force exerted by collision collisions work, energy and power mechanics physics

Two equal masses ${m} _{1}$ and ${m} _{2}$ moving along the same straight line with velocities $+3  {m}/{s}$ and $-5  {m}/{s}$ respectively collide elastically. Their velocities after the collision will be respectively :

  1. $+4 {m}/{s}$ for both
  2. $-3 {m}/{s}$ and $+5 {m}/{s}$
  3. $-4 {m}/{s}$ and $+4 {m}/{s}$
  4. $-5 {m}/{s}$ and $+3 {m}/{s}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As ${m} _{1} = {m} _{2}$, therefore after elastic collision velocities of masses gets interchanged.

Multiple choice force exerted by collision collisions work, energy and power mechanics physics

A machine gun of mass 5 kg fires 30 bullets, each of mass 50 g, per minute at a speed of $400\,m\,{s^{ - 1}}$. What force must be exerted to keep the machine gun in position?

  1. $30N$
  2. $10N$
  3. $27N$
  4. $33N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mass of the gun $=5kg$

Mass of bullets $=50g$
speed at which the bullet is fired$=400m/s$
Therefore$,$ force required to keep the machine gun in position $=\frac{{ch\arg e\,in\,momentum\,of\,bullets}}{{time\,taken}}$
$=\frac{{\left( {50 \times {{10}^{ - 3}} \times 30} \right) \times 400}}{{60}} = 10\,N$
Hence,
option $(B)$ is correct answer.