A car decelerates from 20 m/s to 0 m/s with mass 900 kg. How much kinetic energy is lost?

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Multiple Choice

A car decelerates from 20 m/s to 0 m/s with mass 900 kg. How much kinetic energy is lost?

This question tests how kinetic energy changes as speed changes. Kinetic energy is 1/2 m v^2, so the car’s energy at the start is 1/2 × 900 × (20)^2 = 180,000 J. At the end, the speed is 0, so the final kinetic energy is 0 J. The energy lost equals the initial energy minus the final energy, which is 180,000 J. That energy is transformed into heat and other forms by the brakes and surrounding air.

This question tests how kinetic energy changes as speed changes. Kinetic energy is 1/2 m v^2, so the car’s energy at the start is 1/2 × 900 × (20)^2 = 180,000 J. At the end, the speed is 0, so the final kinetic energy is 0 J. The energy lost equals the initial energy minus the final energy, which is 180,000 J. That energy is transformed into heat and other forms by the brakes and surrounding air.

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