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CBSE Class 9 Science Question 3 of 25

Force and Laws of Motion — Question 3

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Question

Question A3

A hammer of mass 500 g, moving at 50 ms-1, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer?

Answer

Given,

Mass of the hammer (m) = 500 g

Convert g into kg

1000 g = 1 kg

500 g = 5001000\dfrac{500}{1000} = 0.5 kg

Initial velocity of the hammer (u) = 50 ms-1

Terminal velocity of the hammer (v) = 0

Time period (t) = 0.01 s

As per the first equation of motion,

a = v - ut\dfrac{\text{v - u}}{\text{t}}

Substituting we get,

a = 0−500.01\dfrac{0-50}{0.01} = -5000 ms-2

We know, Force = mass x acceleration

Substituting we get,

F = 0.5 x 5000 = -2500 N

According to the third law of motion, the nail exerts an equal and opposite force on the hammer and as the force exerted on the nail by the hammer is -2500 N, hence, the force exerted on the hammer by the nail will be 2500 N.