Question

7. A hammer of mass 400 g, moving at v ms-1, strikes a nail. The nail stops the hammer in a very short time of 0.015 s. If the force generated is – 1680N, find v.

Answer 1

Answer:

Initial velocity of the hammer, u = v m/s

Final velocity of the hammer, v = 0 m/s

Time taken by the hammer to stop = 0.015 s

Acceleration of the hammer = ( v - u ) / t

= ( 0 - v ) / 0.015

= - v / 0.015 m/s^2

Mass of the hammer = 400 g = 0.4 kg

Force generated = - 1680 N

We know that f = ma

Putting the values of f, m and a in the above equation :-

- 1680 = 0.4 × - v / 0.015

- 1680 = - 0.4v / 0.015

- 1680 × 0.015 = - 0.4v

- 25.2 = - 0.4v

v = - 25.2 / - 0.4r

v = 63 m/s

Ans. The value of v is 63 m/s i.e., the hammer was moving with a speed of 63 m/s.