NECO 2005 Physics · Question 11

Which of the statements is/are true of two bodies involved in an inelastic collision? After collision. I. the…

Question

Which of the statements is/are true of two bodies involved in an inelastic collision? After collision. I. the kinetic energy increases II. The momentum decreases III. Their velocities are the same.

A.I only
B.II Only
C.III only
D.I and II only
E.II and III only

Answer: C. III only

Explanation written with AI and checked against the answer key

Analyze the question: We need to decide which statements are true for two bodies in an inelastic collision.

Concept:

In every collision (elastic or inelastic), total momentum is conserved (if no external force acts).
In an elastic collision, kinetic energy is also conserved.
In an inelastic collision, kinetic energy is not conserved. Some is converted to heat, sound, or deformation, so it decreases.
In a perfectly inelastic collision, the bodies stick together and move with a common velocity. This is the textbook meaning of "inelastic collision" in the NECO/JAMB syllabus.

Checking each statement:

I. Kinetic energy increases: False. Kinetic energy decreases or is lost, never gained.

II. Momentum decreases: False. Total momentum is conserved.

III. Their velocities are the same: True in the standard textbook case, where the bodies coalesce and move together with a common velocity:

m₁u₁ + m₂u₂ = (m₁ + m₂)v

Only statement III is true (in the sense intended by the question).

Answer: Option C, III only.

Tip: Remember "Momentum is always conserved; kinetic energy is conserved only in elastic collisions." When you see "inelastic", think "stick together, same final velocity, kinetic energy lost."

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