Work, Power and Energy: Power — Variable Force MCQ

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Power — Variable ForceHardQuestion 30437

Question

A body accelerates from rest with F = 3t N (where t is time in seconds). Mass = 2 kg. Power at t = 4 s is:

A
96 W
Correct
B
12 W
C
48 W
D
24 W

Correct answer

96 W

Explanation

a = F/m = 3t/2. v = ∫a dt = 3t²/4. At t = 4: F = 12 N, v = 12 m/s. P = Fv = 12×12 = 144 W. (Alternatively: v = ∫₀⁴(3t/2)dt = [3t²/4]₀⁴ = 12 m/s. P = 12×12 = 144 W.)

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