# A Motorcar Of Mass 1200 Kg Is Moving Along A Straight Line With A Uniform Velocity Of 90 Km/H. Its Velocity Is Slowed Down To 18 Km/H In 4 S By An Unbalanced External Force. Calculate The Acceleration And Change In Momentum. Also, Calculate The Magnitude Of The Force Required.

Given:

Time taken, t = 4 seconds

Mass of the motor car, m = 1200 kg

Initial velocity of the motor car, u = 90 km/h = 25 m/s

Final velocity of the motor car, v = 18 km/h = 5 m/s

$$\Delta P = mv – mu \\ = \Delta P = 1200 * 5 – 1200 * 25 \\ = – 24000 kg m/s \\ V = u + at \\ = 5 = 25 + a * 4 \\ = a = – 5 m/s^{2} \\ \left | F \right | = m \left | a \right | \\ =1200 * 5 \\ = 6000 N$$

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