12 past paper MCQs on Elastic and Inelastic Collisions, from the Force and Motion unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.In an elastic collision the total kinetic energy: (MDCAT 2024)
Correct answer: (d) before and after the collision remains the same
An elastic collision is defined as one in which the kinetic energy is conserved.
2.If a body having mass m1 (2 kg), moving with 5 m/s approaches another mass, m2 (3 kg) with speed of 1 m/s in same direction, relative speed of approach is 4 m/s. Relative speed of separation after collision will be: (UHS MDCAT 2025)
Correct answer: (a) 4 m/s
In a perfectly elastic collision the relative speed of separation equals the relative speed of approach.
3.A body of mass 2 kg moving with velocity 3 m/s collides with a body of mass 1 kg at rest. If they stick together, their common velocity after collision is: (SZABMU MDCAT 2025)
Correct answer: (b) 2 m/s
Momentum is conserved, so $2\times3$ is shared by $3\,\mathrm{kg}$, giving $2\,\mathrm{m\,s^{-1}}$.
4.In an elastic collision the total kinetic energy (UHS MDCAT 2024)
Correct answer: (d) Before and after collision remains the same
A collision is called elastic precisely because the kinetic energy is the same before and after.
5.A car in motion hits and gets crashed into a tree trunk, what is NOT conserved? (KMU MDCAT 2024)
Correct answer: (a) Kinetic energy alone
The crash is inelastic: momentum still holds, but kinetic energy goes into deformation and heat.
6.Two balls collide each other, it has been observed that the collision is elastic. Which statement is advocates the observation? (SZABMU MDCAT 2023)
Correct answer: (a) K.E before collision = K.E after collision
Momentum is conserved in every collision; it is the kinetic energy that marks an elastic one.
7.Two bodies having same mass undergo elastic collision then their velocities after collision will be: (SZABMU MDCAT 2023)
Correct answer: (d) v1' = v2 v2' = v1
Equal masses in a head-on elastic collision simply exchange velocities.
8.In perfectly elastic collision: (NUMS MDCAT 2023)
Correct answer: (d) Momentum, kinetic energy and total energy, all are conserved
Momentum, kinetic energy and total energy are all conserved in a perfectly elastic collision.
9.A wagon weighing 1000kg is moving with a velocity 50 km/h on smooth horizontal rails. A mass of 250kg is dropped into it. The velocity with which it moves in km/h now is: (PMC MDCAT 2022)
Correct answer: (c) 40 km/h
$1000\times50=1250v$, so $v$ is $40\,\mathrm{km\,h^{-1}}$.
10.Q.76 An elastic collision is the one in which: (NUMS MDCAT 2022)
Correct answer: (a) Kinetic energy and momentum is conserved
In a perfectly elastic collision both the momentum and the kinetic energy are conserved.
11.A particle of mass ‘m’ is projected from the ground with an initial speed u0 at an angle ‘α’ with the horizontal. At the highest point of its trajectory, it makes a completely in-elastic collision with another particle of mass ‘m’ which was thrown vertically upward from the ground with the same initial speed u0. The angle that the composite system makes with the horizontal immediately after the collision is? (PMC Practice 2021)
Correct answer: (a) 45°
At the top one particle carries $mu_0\cos\alpha$ horizontally and the other the same magnitude vertically, so the pair moves at $45^{\circ}$.
12.If two objects of equal masses ‘m’ are moving towards each other with the same speeds ‘v’ then what will be the total final momentum after elastic head-on collision? (UHS MDCAT 2019)
Correct answer: (d) 0 kg m/s
The two momenta are equal and opposite, so their sum is zero before and after.