How is work calculated in the presence of friction?

Work done in the presence of friction is calculated by multiplying the force applied by the distance moved.

When an object moves on a surface, friction opposes its motion. This means that some of the energy used to move the object is converted into heat and sound, rather than being used to do work. The amount of work done in the presence of friction can be calculated by multiplying the force applied by the distance moved. However, the force used must be the net force, which takes into account the force of friction.

For example, if a force of 10N is applied to move an object a distance of 5m on a surface with a coefficient of friction of 0.2, the net force can be calculated as follows:

Frictional force = coefficient of friction x normal force
= 0.2 x (mass x gravity)
= 0.2 x (10kg x 9.81m/s^2)
= 19.62N

Net force = applied force - frictional force
= 10N - 19.62N
= -9.62N

Since the net force is negative, this means that the force of friction is greater than the applied force, and the object will move in the opposite direction. The work done in this case can be calculated as follows:

Work done = force x distance
= -9.62N x 5m
= -48.1J

The negative sign indicates that the work done is negative, which means that energy has been lost due to friction.