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Question 7

A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, then calculate:

(a) the net accelerating force;
(b) the acceleration of the train; and
(c) the force of wagon 1 on wagon 2.

Answer

Mass of engine = 8000 kg

Mass of 1 wagon = 2000 kg

Mass of 5 wagons = 2000 x 5 = 10000 kg

Force exerted by the engine, F = 40000 N

Frictional force offered by the track, Ff = 5000 N

(a) Net force, Fa = Force of engine - Force of friction = F − Ff

      = 40000 − 5000 = 35000 N

Hence, the net accelerating force is 35000 N.

(b) Total mass of the train, M = mass of 5 wagons + mass of engine

      = 10000 + 8000 = 18000 kg

From Newton’s second law of motion:

Force = Mass x acceleration

35000 = 18000 x a

a = 35000 / 18000 = 1.94 m/s2

Hence, the acceleration of the train is 1.94 m/s2.

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