Tag: collisions

Questions Related to collisions

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 :

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

  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 $+3 {m}/{s}$

Show answer
Correct Option: D
Explanation:

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

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?

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

  1. $30N$

  2. $10N$

  3. $27N$

  4. $33N$

Show answer
Correct Option: B
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.

When a ball collides head-on and elastically with an identical ball on a horizontal frictionless surface,comes to rest while the second one moves with the same velocity as that of the first ball before coillision . 

modelling collisions collisions momentum work, energy and power physics

  1. Can be derived by using momentum conservation alone.

  2. Can be derived by using energy conservation alone

  3. cannot be derived by using any to the two conservation principles.

  4. Can be derived by using both conservation of energy and momentum

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Correct Option: A

A ball 'A' of mass 100 gm moving at 2m/s collides with another identical ball 'B' at 3m/s along the same line. There is no loss in energy collision. then, the speed of the balls 'A' and 'B' after the collision are ?

modelling collisions collisions momentum work, energy and power physics

  1. 1m/s and 4m/s

  2. 2m/s and 3 m/s

  3. 3 m/s and 2 m/ s

  4. 2.5 m/s and 2.5 m/s

Show answer
Correct Option: B

Two bodies A and B of masses 5 kg and 10 kg moving in free space in opposite directions with velocity form for second and 0.5 m per second respectively undergo a head on collision the force f of their mutual interaction varies with time T according to the given graph what can you conclude from the given information

modelling collisions collisions momentum work, energy and power physics

  1. Period of Di formation is 0.2 second

  2. Coefficient of restitution is 0.5

  3. Body 0.5 m per second in the original direction

  4. Body be will 1.75 M per second in the reverse direction

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Correct Option: A

A solid cylinder of mass 'M' and radius 'R' is rotating along its axis with angular velocity $\omega $ without friction. A particle of mass 'm' moving with velocity v collide against the cylinder and sticks to its rim. After the impact calculate angular velocity of cylinder.

modelling collisions collisions momentum work, energy and power physics

  1. $\cfrac { I+R\omega }{ I+m{ R }^{ 2 } } $

  2. $\cfrac { mvR+IR }{ I+m{ R }^{ 2 } } $

  3. $\cfrac { I\omega +mvR }{ I+m{ R }^{ 2 } }$

  4. $\cfrac { I\omega +mR }{ I+mv{ R }^{ 2 } } $

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Correct Option: C

A ball is dropped on the floor from a height of $10m$. It rebounds to a height of $2.5\ m$. If the ball is in contact with the floor for $0.01\ s$, then the average acceleration during contact is nearly.

modelling collisions collisions momentum work, energy and power physics

  1. $500\sqrt {2}m/s^{2} upwards$

  2. $1800\sqrt {2}m/s^{2} downwards$

  3. $1500\sqrt {2}m/s^{2} upwards$

  4. $1500\sqrt {2}m/s^{2} downwards$

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Correct Option: A

Which of the following statements are correct

modelling collisions collisions momentum work, energy and power physics

  1. Collision does not require physical contact

  2. Collision between sub atomic particles is elastic

  3. Collision between macroscopic bodies is generally inelastic

  4. None of these

Show answer
Correct Option: A
Explanation:

Collision does not require physical contact because if we go by definition of collision is the meeting of particles or of bodies in which each exerts a force upon the other causing exchange of energy and momentum. In short we can say that collision is a event in which two bodies, exert force on each other for a relative short time. however mostly he study collision in terms of physical contact since force applied is mechanical force. Mostly force between two bodies if it is not physical then it would not be studied as collision more as force applied to bodies.

Choose the incorrect statement

modelling collisions collisions momentum work, energy and power physics

  1. Physical contact is not necessary for a collision

  2. Heat is a form of energy that resided in a system

  3. Kinetic energy of a system may increases due to collision

  4. Work done by internal forces may not be zero

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Correct Option: B

Which of the following is not an inelastic collision.

modelling collisions collisions momentum work, energy and power physics

  1. a man jumps on cart.

  2. a bullet imbedded in a block.

  3. collision of two glass balls.

  4. none of these.

Show answer
Correct Option: C
Explanation:

"Man jumping on cart" and "bullet imbedded in a block" are examples when two bodies have to move together after collision, therefore both of them are inelastic collision.
Where as it is not the case for "collision of two glass balls".