A bullet of mass `10` g is fired horizontally into a `4` kg wooden block resting on a horizontal surface. The coefficient of kinetic friction between the block and the surface is `0.25`. The bullet is embadded the block and the combination moves a distance of `20` m before coming to rest. Find the speed of the bullet just before striking the block. `(g=10m//s^(2))`

Explanation

To find the speed of the bullet just before striking the block, we can follow these steps:

### Step 1: Understand the problem
We have a bullet of mass \( m_b = 10 \, \text{g} = 0.01 \, \text{kg} \) fired into a wooden block of mass \( m_B = 4 \, \text{kg} \). The bullet embeds itself into the block, and they move together after the collision. The coefficient of kinetic friction between the block and the surface is \( \mu = 0.25 \). The block and bullet combination moves a distance of \( s = 20 \, \text{m} \) before coming to rest.

### Step 2: Calculate the deceleration due to friction
The frictional force \( F_f \) acting on the block and bullet combination can be calculated as:
\[
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