# Physics

A car of mass 500kg travelling at 36km/hr brought to rest over a distance of 20m calculate 1.The average ation 2.The average braking force

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1. 36 km/hr = 10 m/s

average braking velocity = (10 m/s + 0) / 2 = 5 m/s

braking time = 20 m / 5 m/s = 4 s

ave acceleration = 10 m/s / 4 s = 2.5 m/s^2
... this would be negative to the direction of travel

work done by the braking force equals the initial kinetic energy of the car

f * 20 m = 1/2 * 500 kg * 10 m/s

f = 125 N

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