Question

A bullet of mass 10 g travelling horizontally with a velocity of
150 m s-l 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 1

In the second part you will apply newtons third law and thus the force exerted by bullet on wooden block will be equal to the force exerted by wooden block on bullet!

Answer 2

Answer :-

• Distance of penetration of the bullet into the block is 2.25 metres .

• Force exerted by the wooden block on the bullet is a retarding force of 50 Newtons .

Explanation :-

We have :-

→ Mass of the bullet (m) = 10 g = 0.01 kg

→ Initial velocity (u) = 150 m/s

→ Time taken (t) = 0.03 s

→ Final velocity (v) = 0

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Firstly, let's calculate acceleration of the bullet by using the 1st equation of motion .

v = u + at

⇒ 0 = 150 + (a)0.03

⇒ -150 = 0.03a

⇒ a = -150/0.03

⇒ a = -5000 m/s²

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Now, we can calculate distance of penetration of the bullet into the block by using the 3rd equation of motion.

v² - u² = 2as

⇒ 0 - (150)² = 2(-5000)(s)

⇒ -22500 = -10000s

⇒ s = -22500/-10000

⇒ s = 2.25 m

Finally, we will calculate the required force by using Newton's 2nd law of motion .

F = ma

⇒ F = 0.01(-5000)

⇒ F = -50 N

[Here, -ve sign represents retarding force] .