The work done in the presence of friction is determined by multiplying the net force applied to an object by the distance it moves.

When an object slides over a surface, friction acts in opposition to its motion. Consequently, some of the energy expended to move the object is transformed into heat and sound, rather than being utilized for work. To accurately calculate the work done while accounting for friction, it is essential to use the net force, which includes the effects of friction.

For instance, consider a scenario where a force of $10 \, \text{N}$ is applied to move an object a distance of $5 \, \text{m}$ across a surface with a coefficient of friction of $0.2$. The net force can be calculated as follows:

1. Calculate the frictional force:

2. Determine the net force:

Since the net force is negative, this indicates that the force of friction exceeds the applied force, causing the object to move in the opposite direction.

3. Calculate the work done:

The negative sign in the work done calculation signifies that energy has been lost due to friction. In essence, the negative work indicates that work is done against the motion of the object, primarily due to the frictional forces at play.