A 2 kg ball and a 4 kg ball are dropped together from the same height. After each falls 30 feet, find the ratio of their respective kinetic energies.
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Question

A 2 kg ball and a 4 kg ball are dropped together from the same height. After each falls 30 feet, find the ratio of their respective kinetic energies.

G1 Physics · Accepted Answer

Step 1 — Principle: The net work on a body equals its change in kinetic energy: Wₙₑₜ = Kf − Ki. Step 2 — Working: Each begins from rest and loses gravitational PE mgh. Step 3 — Working: Because both fall the same distance h, K₁:K₂=m₁:m₂=2:4=1:2. Correct answer: C — 1 : 2.