Question

A bullet is moving with a velocity of 10 m/s striks a wooden plank. It penetrats to the depth of 20cm before comming to a stop. Calculate the average retardation of the bullet while passing through the plank.​

Answer 1

Answer:

The average retardation is $250 m/s^2$.

Explanation:

The velocity with which the bullet is moving is, $u=10m/s$ (initial velocity)

It penetrates to a depth of 20 cm before it comes to rest. hence the distance travelled by bullet, $d=20cm=0.2m$

The final velocity of the bullet is $v=0m/s$,

average retardation can be found from the equation of motion $v^2-u^2=2ad$

⇒  $a=\frac{v^2-u^2}{2d}$

⇒$a=\frac{0-100}{2*0.2}=-250m/s^2$

Hence the acceleration of the bullet is $250m/s^2$. The negative sign indicates negative acceleration which is called retardation.