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

(a) Given,

Force of engine = 40,000 N


Force of friction = 5,000 N


So,


Net accelerating force, F = Force of engine – Force of friction


= 40000 – 5000


= 35000 N


(b) Net force exerted by the engine = 35000 N


The mass of 1 wagon of train = 2000 kg


The mass of 5 wagons of train = 2000 × 5


= 10000 kg


In other words, the mass of whole train is 10000 kg


We know that,


Net force = mass of train × acceleration


F = m × a


35000 = 10000 × a


a = m/s2


a = 3.5 m/s2


Therefore, the acceleration of the train is 3.5 m/s2


(c) There are total 5 wagons behind the engine (which have been marked 1, 2, 3, 4 and 5 in the figure) and there are only 4 wagons behind wagon 1.



Force of wagon 1 = Mass of 4 wagons × Acceleration of train


= 2000 × 4 × 3.5


= 28000 N


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