Question 1

In a perfectly INELASTIC collision, the two bodies:

Accepted Answer

Stick together and move with a common velocity; KE is lost but momentum is conserved. Sticking = maximum possible KE loss consistent with momentum conservation. Momentum is still exactly conserved.

Question 2

In ANY collision between two bodies (no external force), which is ALWAYS conserved?

Accepted Answer

Total linear momentum. Momentum conservation needs only F_ext = 0. KE survives only the elastic case — the single most-tested distinction.

Question 3

A 2 kg body at 6 m/s hits a 4 kg body at rest and sticks to it. Their common velocity is:

Accepted Answer

2 m/s. v = 2×6/6 = 2 m/s.

Question 4

For that same collision (2 kg at 6 m/s onto 4 kg at rest, perfectly inelastic), the kinetic energy LOST is:

Accepted Answer

24 J. KE_i = 36 J; KE_f = ½×6×4 = 12 J; loss = 24 J (two-thirds!). Shortcut: ΔKE = ½μu² = ½×(8/6)×36 = 24 J.

Question 5

A 10 g bullet at 400 m/s embeds into a 1.99 kg block hanging as a ballistic pendulum. The height to which the block+bullet swings is:

Accepted Answer

0.2 m. v_common = 0.01×400/2 = 2 m/s; h = v²/2g = 4/20 = 0.2 m. Trap: never equate bullet KE to mgh — most KE is lost in embedding.

Question 6

Two identical cars moving at equal speeds v collide head-on and lock together. The wreckage moves at:

Accepted Answer

Zero. Equal and opposite momenta cancel: the combined wreck stops; ALL the kinetic energy is dissipated.

Question 7

A 3 kg lump of clay at 4 m/s hits a 1 kg block at rest and sticks. The common speed is:

Accepted Answer

3 m/s. v = 12/4 = 3 m/s.

Question 8

In a perfectly inelastic head-on collision of equal masses (one at rest), the fraction of the initial KE lost is:

Accepted Answer

1/2. v' = u/2 ⇒ KE_f = ½(2m)(u/2)² = mu²/4, while KE_i = mu²/2. So exactly half the kinetic energy is lost.

Inelastic & Perfectly Inelastic Collisions — NEET Physics MCQs with Solutions

Questions with solutions