### Solution to problems – class 9 – Set 1 Q 28

##### June 5, 2019

## Problem Statement

**A bullet is moving at a speed of 350 m/s when it embeds into a lump of moist clay. The bullet penetrates for a distance of 0.05 m. Determine the acceleration of the bullet while moving into the clay. (Assume a uniform acceleration.)**

## Solution to physics problem

**Initial velocity of the bullet U=350 m/s****Final velocity of the bullet = 0****Distance travelled to acquire the final velocity =S=0.05 m**

To find out the acceleration (here it is negative acceleration or retardation actually), we will use the equation of retardation

**V ^{2} = U^{2} – 2 a S**

As V = 0, the equation becomes: U^{2} = 2 a S

Which gives retardation a = U^{2} / (2 S) = 350^{2}/(2 x 0.05) =1225000 m/s^{2}

**So the answer would be: retardation =1225000 m/s**

^{2}**Alternate way:**

Here we will use the general equation of acceleration.

**V ^{2} = U^{2} + 2 a S**

As V = 0, the equation becomes: U^{2} = – 2 a S

Which gives acceleration a = – U^{2} / (2 S) = – 350^{2}/(2 x 0.05) =- 1225000 m/s^{2}

So the answer would be: acceleration =- 1225000 m/s^{2}

The negative sign indicates that its actually retardation.