A wire of length L and radius r extends by l under force f. Another wire of the same material has length 2L and radius 2r and is pulled by force 2f. Its extension is:
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Question

A wire of length L and radius r extends by l under force f. Another wire of the same material has length 2L and radius 2r and is pulled by force 2f. Its extension is:

G1 Physics · Accepted Answer

For a wire: ΔL = FL/(AY) For the same material, Y is constant. Therefore: ΔL₂/ΔL₁ = (F₂L₂/A₂)/(F₁L₁/A₁) = (2f × 2L)/(f × L) × [πr²/π(2r)²] = 4 × 1/4 = 1 Thus: ΔL₂ = l Hence option C.