Question

A bullet of mass 0.05 kg strikes a wooden plank with a velocity of 200 m/s and emerges from it with a velocity of 50 m/s. Calculate the work done by the resistive force offered by the plank.

Answer 1

The difference in the kinetic energy before the strike and after the strike is equal to the work done by the resistive force offered by the plank

1÷2×M×(u - v) = 1÷2×0.05×150=3.75J

Answer 2

The work done by the resistive force offered by the plank is 937.5 Joules.

Explanation:

Given that,

Mass of the bullet, m = 0.05 kg

Initial speed of the bullet, u = 200 m/s

Final speed of the bullet,. v = 50 m/s

To find,

The work done by the resistive force offered by the plank.

Solution,

It is a case of work energy theorem. The work done by the resistive force offered by the plank is given by :

$W=\dfrac{1}{2}m(v^2-u^2)$

$W=\dfrac{1}{2}\times 0.05\times ((50)^2-(200)^2)$

W = -937.5 Joules

So, the work done by the resistive force offered by the plank is 937.5 Joules.

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