Q22 of 49 Page 9

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, let us consider the complete train as single body on which a force of 40000 N is applied by engine of mass 8000 kg on which a opposing force(friction force) is applied in direction opposite to direction of motion of body.

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

= 40000 – 5000

= 35000 N


(b)
given:
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

The  mass of engine = 8000 kg
The mass of train = 10000 +8000 =18000 kg

We know that,

Net force = mass of train × acceleration

F = m × a

35000 = 18000 × a

a =  m/s2  = 1.9444 m/s2

Therefore, the acceleration of the train is 1.9444 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

                              (Behind Wagon 1)


= 2000 × 4 × 1.9444  (We know that weight of one Wagon is 2000 kg)

= 15555.2 N
Thus, the force of Wagon 1 on Wagon 2 is 15555.2 N

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