**Introduction**
To find the resistance given by wood against a bullet, we can calculate the work done by the wood in stopping the bullet. The work done can be determined using the formula:

Work = Force * Distance

We know the distance the bullet penetrates into the wooden block, so we need to find the force applied by the wood to stop the bullet.

**Calculating Force**
To calculate the force, we can use the formula:

Force = Mass * Acceleration

The acceleration can be determined using the equation:

Acceleration = (Final Velocity^2 - Initial Velocity^2) / (2 * Distance)

Given:
Mass of the bullet (m) = 25 g = 0.025 kg
Initial velocity (u) = 200 m/s
Distance penetrated (d) = 5 cm = 0.05 m

**Calculating Acceleration**
Acceleration = (Final Velocity^2 - Initial Velocity^2) / (2 * Distance)
Since the bullet comes to a stop, the final velocity (v) is 0.
Acceleration = (0 - 200^2) / (2 * 0.05)
Acceleration = -40000 m/s^2

**Calculating Force**
Force = Mass * Acceleration
Force = 0.025 kg * (-40000 m/s^2)
Force = -1000 N

**Interpreting the Negative Sign**
The negative sign indicates that the force applied by the wood is in the opposite direction to the initial motion of the bullet. This is because the wood resists the motion and brings the bullet to a stop.

**Conclusion**
The resistance given by wood against the bullet is calculated to be -1000 N. The negative sign indicates that the force applied by the wood is opposite to the initial motion of the bullet.