Force and Laws of Motion - NCERT Solutions (Part 6) | 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 6)
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00:00 Introduction
00:27 NCERT Solutions: Question 1
09:15 NCERT Solutions: Question 2
14:16 NCERT Solutions: Question 3
17:34 NCERT Solutions: Question 4
24:26 NCERT Solutions: Question 5
28:09 Website Overview
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Points covered in this video:-

Question 1. A bullet of mass 10 g travelling horizontally with a velocity of 150 m s–1 strikes a stationary wooden block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block. Also calculate the magnitude of the force exerted by the wooden block on the bullet.
Answer. We will first calculate the acceleration (or rather retardation) of the bullet.
Now, Initial velocity, u = 150 ms-1
Final velocity, v = 0
And, Time,t = 0.03 s
Now, v = u + at
0 = 150 + a x 0.03
0.03 a = -150
a = -150/0.03
a = -5000 ms-2

Let us calculate the distance of penetration of bullet now,
We know that; v2 = u2 + 2as
(0)2 = (150)2 + 2 x (-5000) x s
0 = 22500 - 10000 x s
10000s = 22500
s = 2.25 m
Thus, the distance of penetration of the bullet into the block of wood will be 2.25 meters.
We will now calculate the magnitude of force. Now,
Forec, F = m x a
F = 10/1000 X (-5000)
F = 50 N
Thus, the magnitude of force exerted by the wooden block on the bullet is 50 newtons. .