Work, in physics, is the energy transferred when a force exerted on an object causes it to be moved over some distance. The amount of work done by a force is calculated by multiplying the distance over which the object is moved by the force. In this equation, the force is called f and the distance is called d.
There are many things to consider when determining whether a given force does work on an object. First, the force must be in the same direction as the object moves. If the force is in the opposite direction, no work will be done. This is because the object is displaced and the force does not cause the displacement.
Another thing to consider is the angle between the force and the displacement. If the angle is 0 degrees or 90 degrees, work is done. However, if the angle is not 0 degrees or 90 degrees, then a different formula needs to be used.
In a circular motion, for example, the centripetal force exerted by the string on the ball inwards is zero work. This is because the centripetal force is perpendicular to the ball’s velocity.
If the centripetal force is parallel to the ball’s velocity, then the same force is positive and does work on the ball. In this case, the total amount of work is equal to the mass of the ball multiplied by the acceleration of the ball.
The same can be said of any other forces that have a component in the same direction as the displacement of the object, such as the centrifugal force exerted by a spring on a spinning wheel. These forces do not transfer energy to the wheel.
Some other examples include the internal force that is applied on a rope in a pulley system or the centripetal force exerted on a ball in uniform circular motion sideways. These forces do not transfer energy to the ball or to the system.
These examples also illustrate the point that if the force is not in the same direction as the object’s movement, then no work will be done. The picture below illustrates this point.
This is why the kids who are playing football in the picture on the left are doing work, while the teen who is studying for an exam isn’t. The difference in how work is defined in physics and everyday language can explain why the kids are having fun while the teen is working.
It is interesting to note that the teen in the picture on the right is not doing any work at all. This is because she isn’t moving anything, so there is no corresponding displacement to be calculated.
The unit of work is the joule (J). In a meter, one joule is equivalent to 1 N * m. This is because one J is the energy expended when a force of one newton acts on an object that is displaced a distance of one meter.