A 10 g bullet leaves a rifle at speed 1000 m s⁻¹ and strikes Earth at the same level at speed 500 m s⁻¹. Find the magnitude of work needed to overcome air resistance.
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A 10 g bullet leaves a rifle at speed 1000 m s⁻¹ and strikes Earth at the same level at speed 500 m s⁻¹. Find the magnitude of work needed to overcome air resistance.

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: At equal heights there is no net change in gravitational PE. Step 3 — Working: Energy lost due to drag is ½m(u²−v²)=½(.01)(1000²−500²)=3750 J. Correct answer: B — 3750 J.