20 Momentum Quiz Questions and Answers

Question 1:
What is the definition of momentum in physics?
A) Mass divided by velocity
B) Mass multiplied by velocity
C) Velocity divided by time
D) Force multiplied by time

Answer: B) Mass multiplied by velocity
Explanation: Momentum is defined as the product of an object’s mass and its velocity, calculated as p = m * v, where p is momentum, m is mass, and v is velocity.

Question 2:
What are the SI units of momentum?
A) kg/m
B) m/s
C) kg·m/s
D) N·s

Answer: C) kg·m/s
Explanation: The SI unit of momentum is derived from p = m * v, so it is kilogram times meters per second (kg·m/s).

Question 3:
If a 2 kg object is moving at 3 m/s, what is its momentum?
A) 5 kg·m/s
B) 6 kg·m/s
C) 1.5 kg·m/s
D) 9 kg·m/s

Answer: B) 6 kg·m/s
Explanation: Momentum is calculated as p = m * v = 2 kg * 3 m/s = 6 kg·m/s.

Question 4:
Which of the following statements is true about the conservation of momentum?
A) Momentum is always conserved in elastic collisions only
B) Momentum is conserved in isolated systems with no external forces
C) Momentum increases in inelastic collisions
D) Momentum is not conserved in any collision

Answer: B) Momentum is conserved in isolated systems with no external forces
Explanation: In an isolated system where no external forces act, the total momentum before and after an event remains constant, as per the law of conservation of momentum.

Question 5:
In a head-on elastic collision between two objects of equal mass, where one is at rest, what happens to their velocities?
A) They exchange velocities
B) The moving object stops, and the stationary one moves with the same velocity
C) Both objects stop
D) The moving object continues with double speed

Answer: A) They exchange velocities
Explanation: In an elastic collision between two objects of equal mass, with one at rest, the objects swap their velocities due to the conservation of momentum and kinetic energy.

Question 6:
What is impulse in relation to momentum?
A) Change in velocity
B) Force applied over time
C) Product of mass and acceleration
D) Change in momentum

Answer: D) Change in momentum
Explanation: Impulse is equal to the change in momentum of an object, given by J = F * Δt = Δp, where J is impulse, F is force, and Δt is time.

Question 7:
A 5 kg ball moving at 4 m/s collides with a stationary 3 kg ball. If the collision is perfectly inelastic, what is the combined velocity after collision? (Assume no external forces)
A) 2 m/s
B) 1.5 m/s
C) 4 m/s
D) 2.5 m/s

Answer: A) 2 m/s
Explanation: In a perfectly inelastic collision, momentum is conserved. Total initial momentum = 5 kg * 4 m/s + 3 kg * 0 m/s = 20 kg·m/s. Combined mass = 8 kg. Final velocity = 20 kg·m/s / 8 kg = 2 m/s.

Question 8:
Which factor does NOT affect the momentum of an object?
A) Mass
B) Velocity
C) Color
D) Acceleration

Answer: C) Color
Explanation: Momentum depends only on mass and velocity (p = m * v); properties like color do not influence it.

Question 9:
If a car doubles its speed, how does its momentum change, assuming mass is constant?
A) It halves
B) It stays the same
C) It doubles
D) It quadruples

Answer: C) It doubles
Explanation: Momentum is directly proportional to velocity. If velocity doubles, momentum also doubles, as p = m * v.

Question 10:
In which scenario is momentum not conserved?
A) A rocket in space expelling fuel
B) Two billiard balls colliding on a table
C) A car crashing into a wall
D) An isolated explosion in space

Answer: C) A car crashing into a wall
Explanation: External forces (like the wall) act on the system, so momentum is not conserved in that scenario, unlike in isolated systems.

Question 11:
What is the momentum of a photon? (In the context of relativistic physics)
A) Zero, since photons have no mass
B) Equal to its energy divided by the speed of light
C) Infinite
D) Equal to its wavelength

Answer: B) Equal to its energy divided by the speed of light
Explanation: For a photon, momentum p = E/c, where E is energy and c is the speed of light, even though photons are massless.

Question 12:
A 10 kg object at rest is acted upon by a force of 20 N for 5 seconds. What is the final momentum?
A) 50 kg·m/s
B) 100 kg·m/s
C) 200 kg·m/s
D) 0 kg·m/s

Answer: B) 100 kg·m/s
Explanation: Impulse = F * t = 20 N * 5 s = 100 N·s. Impulse equals change in momentum, so final momentum = initial momentum (0) + 100 N·s = 100 kg·m/s.

Question 13:
In an elastic collision, what is conserved besides momentum?
A) Kinetic energy
B) Potential energy
C) Mass
D) Velocity

Answer: A) Kinetic energy
Explanation: In elastic collisions, both total momentum and total kinetic energy are conserved.

Question 14:
If two objects have the same momentum, which statement must be true?
A) They have the same mass
B) They have the same velocity
C) Their masses and velocities are inversely related
D) They are moving in the same direction

Answer: C) Their masses and velocities are inversely related
Explanation: Momentum p = m * v. If p is the same, then m1 * v1 = m2 * v2, meaning mass and velocity can vary as long as their product is equal.

Question 15:
What happens to the momentum of a system during an inelastic collision?
A) It increases
B) It decreases
C) It is conserved if isolated
D) It becomes zero

Answer: C) It is conserved if isolated
Explanation: Even in inelastic collisions, total momentum is conserved in an isolated system, though kinetic energy is not.

Question 16:
A bullet of mass 0.01 kg is fired at 500 m/s. What is its momentum?
A) 5 kg·m/s
B) 0.5 kg·m/s
C) 50 kg·m/s
D) 5 kg·m/s (wait, duplicate option)

Answer: A) 5 kg·m/s
Explanation: Momentum = m * v = 0.01 kg * 500 m/s = 5 kg·m/s. (Note: The duplicate in options is a typo; A is correct.)

Question 17:
How does increasing the mass of an object affect its momentum at a constant velocity?
A) Decreases it
B) Has no effect
C) Increases it proportionally
D) Doubles it

Answer: C) Increases it proportionally
Explanation: Since p = m * v, increasing mass while keeping velocity constant will increase momentum directly.

Question 18:
In a system with two objects colliding, if the total momentum before is 10 kg·m/s, what must be the total momentum after? (Assuming no external forces)
A) Less than 10 kg·m/s
B) More than 10 kg·m/s
C) Exactly 10 kg·m/s
D) Zero

Answer: C) Exactly 10 kg·m/s
Explanation: By the conservation of momentum, the total momentum in an isolated system remains constant.

Question 19:
What is the formula for the change in momentum?
A) Δp = m * Δv
B) Δp = F * t
C) Δp = v * t
D) Both A and B

Answer: D) Both A and B
Explanation: Change in momentum Δp can be expressed as m * Δv (from kinematics) or F * t (from impulse-momentum theorem).

Question 20:
A 4 kg object moving at 2 m/s collides elastically with a 2 kg object at rest. What is the velocity of the 4 kg object after collision?
A) 0 m/s
B) 1 m/s
C) 2 m/s
D) 4 m/s

Answer: A) 0 m/s
Explanation: In an elastic collision between objects of different masses, with one at rest, the initial moving object can stop if masses are in a specific ratio. Here, calculations show the 4 kg object stops, and the 2 kg object moves at 4 m/s, conserving both momentum and kinetic energy.