Question

Two identical spheres move in opposite directions with speeds v₁ and v₂ and pass behind an opaque screen, where they may either cross without touching (event 1) or make an elastic head-on collision (event 2) –

• A. We can never make out which event has occurred
• B. We can not make out which event has occurred only if v₁ = v₂
• C. We can always make out which event has occurred
• D. We can make out which event has occurred only if v₁ = v₂

Answer 1

Answer: (A)

We can never make out which event has occurred

Answer 2

Balls are identical and velocity exchanges if elastic head on collision occurs.