Physics · Science General

Collisions, Momentum and Kinetic Energy

331 Questions

Collisions, momentum, and kinetic energy questions analyze the principles of elastic and inelastic impacts. They require calculating mass, velocity, and conserved energy during physical interactions. These foundational physics topics are essential for most government engineering and general science examinations.

Elastic collisionsInelastic collisionsMomentum calculationKinetic energy principlesVelocity after impact

Collisions, Momentum and Kinetic Energy Questions

Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

A cricket ball of mass 300 g is bowled towards a batsman with a speed of $\displaystyle 180\quad km\quad { h }^{ -1 }$. The batsman hits the ball such that it bounces back with the same speed. If the force exerted by the bat on the ball is 3000 N, find the duration of the impact is ____ s.

  1. 1

  2. 0.01

  3. 0.1

  4. 0.04
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Change in momentum = F * t. Initial velocity = 180 km/h = 50 m/s. Final velocity = -50 m/s. Change in momentum = m * (vf - vi) = 0.3 kg * (-50 - 50) = -30 kg m/s. Magnitude = 30. t = 30 / 3000 = 0.01 s.

Multiple choice modelling collisions collisions momentum work, energy and power physics

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 . 

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When two identical bodies undergo a one-dimensional elastic collision, energy conservation and momentum conservation together are necessary and sufficient to uniquely determine the final velocities, demonstrating that both principles are required.

Multiple choice modelling collisions collisions momentum work, energy and power physics

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 ?

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For an elastic collision between two identical bodies, the velocities are simply exchanged. Ball A initially moving at 2 m/s and Ball B moving at 3 m/s along the same line will swap velocities, meaning Ball A moves at 3 m/s and Ball B moves at 2 m/s after the collision.

Multiple choice modelling collisions collisions momentum work, energy and power physics

Which of the following statements are correct

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice modelling collisions collisions momentum work, energy and power physics

Which of the following is not an inelastic collision.

  1. a man jumps on cart.

  2. a bullet imbedded in a block.

  3. collision of two glass balls.

  4. none of these.
Reveal answer Fill a bubble to check yourself
C Correct answer
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".

Multiple choice modelling collisions collisions momentum work, energy and power physics

In a perfectly elastic collision :

  1. both KE and momentum are conserved.

  2. only KE is covered.

  3. only momentum is covered.

  4. neither KE nor momentum are conserved.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Elastic collisions occur only if there is no net conversion of kinetic energy into other forms. During the elastic collision, kinetic energy is first converted to potential energy associated with a repulsive force between the particles (when the particles move against this force, i.e. the angle between the force and the relative velocity is obtuse), then this potential energy is converted back to kinetic energy (when the particles move with this force, i.e. the angle between the force and the relative velocity is acute).
Also, the average of the momenta before and after the collision is the same. 
Hence, in a perfectly elastic collision both KE and momentum are conserved.

Multiple choice modelling collisions collisions momentum work, energy and power physics

In an elastic collision between two particle :

  1. the total kinetic energy of the system is always conserved.

  2. the kinetic energy of the system before collision is equal to the kinetic energy of the system after collision.

  3. the linear momentum of the system is conserved.

  4. the mechanical energy of the system before collision is equal to the mechanical energy of the system after collision.
Reveal answer Fill a bubble to check yourself
B,C,D Correct answer
Explanation
Total kinetic energy of the system is not conserved always. 
Total kinetic energy of a system is conserved just before and after the collision only in case of perfectly elastic collision.

According to law of conservation of momentum, total linear momentum of the system is always conserved irrespective of elastic or inelastic collision

According conservation of energy, total mechanical energy of a system is always conserved irrespective of elastic or inelastic collision.
Hence total mechanical energy of the system before collision is equal to the mechanical energy of the system after the collision. 
Multiple choice modelling collisions collisions momentum work, energy and power physics

A ball hits the floor and rebound after inelastic collision. In this case :

  1. the momentum of the ball just after the collision is the same as that just before the collision

  2. the mechanical energy of the ball remains the same in the collision

  3. the total momentum of the ball and the earth is conserved

  4. the total energy of the ball and the earth is conserved
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Momentum of the system changes only due to external force (OR impulse).
When a ball hits the floor and gets rebound, then no external force (Impulse) acts on the ball as well as the floor, thus total momentum of the "ball + earth" system remains conserved.
 Also some of the mechanical energy of the ball is always lost in an inelastic collision due to its deformation, hence it cannot remain conserved in this collision.

Multiple choice modelling collisions collisions momentum work, energy and power physics

A ball rebounds after colliding with the floor, then in case of inelastic collision:

  1. The momentum of the ball before and after collision is same.

  2. The mechanical of the ball before and after collision is same.

  3. The total momentum of the earth-ball system is conserved

  4. The total kinetic energy of earth and ball is conserved
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Momentum of Earth ball system is conserved because no external force is acting on the system.

Multiple choice modelling collisions collisions momentum work, energy and power physics

Which of the following statements is true for collisions-

  1. Momentum is conserved in elastic collisions but not in inelastic collisions

  2. Total kinetic energy is conserved in elastic collisions but momentum is not conserved

  3. Total kinetic energy is not conserved in inelastic collisions but momentum is conserved

  4. Total kinetic energy and momentum both are conserved in all types of collisions
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total momentum and total energy of a system always remain conserved.

In inelastic collisions, some of the kinetic energy goes into the heat energy, with total energy and momentum still being conserved.

Multiple choice modelling collisions collisions momentum work, energy and power physics

For inelastic collision between two spherical rigid bodies: 

  1. The total kinetic energy is conserved

  2. The total potential energy is conserved

  3. The linear momentum is not conserved

  4. The linear momentum is conserved
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In any type of collision, linear momentum is conserved, unless external force acts on the system. elasticity determines the loss in KE. elastic => no loss. inelastic => max. loss of KE ($KE _i - KE _{COM}$)

Multiple choice modelling collisions collisions momentum work, energy and power physics

During a pool game the cue ball is shot at the red ball. When the cue ball strikes the red ball, the cue ball stops dead, and the red ball moves away at the same velocity the cue ball had before the collision. The type of collision represented in this example is:

  1. An elastic collision

  2. A perfectly inelastic collision

  3. An inelastic collision

  4. All of the above

  5. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In an elastic collision there is no loss of kinetic energy. If in the given case , balls are of same masses then their kinetic energies will also be same because their velocities are equal and as said , only one ball is moving before and after collision therefore total kinetic energy is constant i.e. it is an elastic collision.

    total kinetic energy before collision= total kinetic energy after collision
                                    $1/2mv^{2}+0=0+1/2mv^{2}$

Multiple choice modelling collisions collisions momentum work, energy and power physics

Identify which of the following quantities remain conserved during an elastic collision?

  1. momentum only

  2. momentum and potential energy

  3. kinetic energy only

  4. momentum and kinetic energy

  5. momentum end velocity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

During collision, net external force acting on the colliding bodies is zero, thus total momentum of the system is conserved in all types of collision.

But total kinetic energy of the system is conserved only in case of elastic collision.
Hence option D is correct.

Multiple choice modelling collisions collisions momentum work, energy and power physics

During one dimensional collision or head on collision :

a) The bodies move along the line joining their centre of mass before and after collision.
b) The bodies should move in opposite direction.
c) The bodies change their direction after collision.
d) The bodies move along the line joining their centre of mass before and after collision either in same direction or in opposite direction.

  1. Only a is correct

  2. Only a & b are correct

  3. a, b & c are correct

  4. Only a and d are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

By the definition of head on collision, the two bodies have to move along the line joining their centers and their velocities can be in any directions (only two possible here).