Work, by definition, is the total change in energy, or the amount of force applied over a distance. During a tennis shot, there is work being performed by two different things. The first thing that performs work on the ball is the racquet. During the time that it is in contact with the ball, the racquet is applying a force of 2.5x10^2 N over a distance of 0.09m. Therefore we can calculate the work using the equation involving force and displacement:
Therefore the amount of work done by the racquet on the ball is 23 J
The second thing that performs work on the ball is gravity. To find the total amount of work done by gravity on the ball, we must find the change in gravitational potential energy from the time the ball leaves the racquet to the time the ball bounces. We can do this by finding the amount of energy at the start and at the end using our potential energy equation, and then by subtracting the initial energy from the final energy:
Therefore the amount of work performed on the ball by gravity is -0.41
We can tell that there is positive work being done by the racquet because the ball accelerates forward, which means there was a force being applied. If there were no force being applied, it would mean that there was no work, but it would also mean that there would be no acceleration, so since there is acceleration, we know that there is work being done. We can tell that work is being done by gravity because the ball falls. If there were no work being done, it would mean that there was no change in energy, and therefore the ball would still be at the same height but since it fell below its initial height, we know that there was negative work being done on the ball.
We can tell that there is positive work being done by the racquet because the ball accelerates forward, which means there was a force being applied. If there were no force being applied, it would mean that there was no work, but it would also mean that there would be no acceleration, so since there is acceleration, we know that there is work being done. We can tell that work is being done by gravity because the ball falls. If there were no work being done, it would mean that there was no change in energy, and therefore the ball would still be at the same height but since it fell below its initial height, we know that there was negative work being done on the ball.
Andy Murray, excited after becoming the first British man to win Wimbledon since 1936