Force and Laws of Motion - NCERT Solutions (Part 5) | Class 9 Physics

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✅ In this video,

✔️ Class: 9
✔️ Subject: Physics
✔️ Chapter: Force and Laws of Motion
✔️ Topic Name: NCERT Solutions (Part 5)
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00:00 Introduction
00:17 Question No. 01
12:18 Question No. 02
18:29 Question No. 03
24:42 Website Overview
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Question 1. 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. (a) the net accelerating force;
Here, the force exerted by the engine is 40000 N and the opposing force of friction offered by the track is 5000N. So,
Net accelerating force, F = Force of engine - Force of friction
= 40000 - 5000
= 35000 N
Thus, the net accelerating force (F) exerted by the engine is 35000 newtons. This force will be used in further calculations.

(b) the acceleration of the train;
We have just calculated that the net force exerted by the engine on the train is 35000 N. now, the mass of 1 wagon of train is 2000 kg, so the mass of 5 wagons of train will be 2000 x 5 = 10000 kg. In order words, the mass of whole train is 18000 kg.
Now, net force = mass of train x acceleration
F = m x a
35000 = 18000 x a
a = 35000/18000 ms-2
a = 1.94 ms-2
Thus, the acceleration of the train is1.94 ms-2
The acceleration of wagons is 3.5 ms-2 .