A 1000 kg car travelling at 20 m/s brakes with a constant force of 4000 N until it stops. What distance does it travel while braking?
Answer and explanation
Correct answer: A. 50 m
- Step 1: Kinetic energy = ½mv² = ½ × 1000 × 400 = 200 000 J.
- Step 2: Work done by the brakes = Fd, so d = 200 000 ÷ 4000 = 50 m.
Answer
50 m.
Why not the others: 2.5 m: the speed was not squared in the kinetic energy. 100 m: the factor ½ was missed. 200 m: the kinetic energy was divided by the mass 1000 instead of the force.
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