Question

a bullet of mass 20 g moving with a velocity of 500m/s strikes a tree and goes out from the other side with a velocity of 400m/s calculate the work done by the bullet in joule in passing through he tree​

Answer 1

Given :

Mass of bullet = 20g

Initial velocity = 500m/s

Final velocity = 400m/s

To Find :

Work done by the bullet.

Solution :

■ As per work - kinetic energy theorem, work done by object is always equal to the change in kinetic energy.

• W = ∆k

We know that, kinetic energy of body of mass m moving at a speed of v is given by

• k = 1/2 mv²

Conversion :

We know that, 1000g = 1kg

∴ 20g = 20/1000 = 0.02kg

By substituting the given values;

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

$:\implies\sf\:W=\dfrac{1}{2}(0.02)[(500)^2-(400)^2]$

$:\implies\sf\:W=(0.01)[250000-160000]$

$:\implies\sf\:W=(0.01)[90000]$

$:\implies\bf\:W= 900\:J$