Non-conservative force is the force that incorporates a significant change in mechanical energy. This means that the work done by a non-conservative force adds or removes a part of mechanical energy. It does not depend on the path followed by a moving particle, but it depends on the initial and final velocity of the object. The work done by a non-conservative force is irreversible in nature. If the particle moves in a closed path, then the work done by a non-conservative force is not equal to zero.
Examples of Non-Conservative Force
1. Moving a Block
While moving a block between two points, the path followed by the block has to be taken into consideration. This is because the amount of friction depends on the path followed by the block. The work done against the force of friction when a long path is taken is more than the work done if the short path has been chosen. Hence, the existence of a non-conservative force can be easily observed.
2. Rubbing Hands
When we rub our hands against each other, a considerable amount of heat energy is produced. This is because the force applied to rub the hands together gets opposed by a force of friction. The frictional force resists the motion and dissipates the energy produced by the applied force in the form of heat energy. The conversion of mechanical energy into heat energy implies the existence of a non-conservative force.
3. Rolling a Ball
A ball rolling on the ground eventually comes to rest after some time. This happens because the motion of the ball gets opposed by the force of friction. The frictional force tends to remove a portion of the applied mechanical force and dissipate the energy produced by it. In this case, the work done is irreversible in nature. Hence, the force acting on the ball is known as a non-conservative force.
4. Pulling a Rope
A rope fixed at one end and free to move at the other end is susceptible to build a significant amount of tension in it by pulling the loose end. The pull force applied to the free end depends on the path followed by it. If the rope is pulled directly, then the magnitude of the tension force is different than the value or the intensity of tension built in the rope when it is pulled via a pulley mechanism. Hence, the tension force is a prime example of non-conservative force.
5. Back and Forth Movement of an Object
When an object is made to move from point A to point B, then a value of work done by that particular object against the force of friction is observed. While retracing the path of the object, i.e., while moving the object back from point B to point A, again a value of work done is observed. The total magnitude of the work done is equal to the algebraic sum of individual work values observed in both cases. Hence, the work done is independent of the path taken and is not equal to zero when the initial and final points of the motion coincide with each other; therefore, the force in action is known as non-conservative force.
When a person moves on a slippery floor, he tends to lose balance and skid on the surface. This is because the value of the frictional coefficient is less on slippery surfaces. The force of friction; therefore, adds value to the mechanical motion of the body by increasing its speed. Hence, skidding is a prominent example of non-conservative force.