Transformation of Energy
So, we found that gravitational potential energy can be transformed into kinetic energy and back into gravitational potential energy again. As the skater moves from the top of his path downward, the system's gravitational potential energy is being transformed into kinetic energy. As he moves upward from the bottom of the track, his kinetic energy is being transformed into gravitational potential energy.
In addition, we found that the system's gravitational potential energy is greatest when the skater is at the top of his path, and we found that the gravitational potential energy is zero when the skater is at the bottom of the track (if we set the blue dotted gravitational potential energy reference marker at the bottom of the track). We found that the system's kinetic energy is zero at the top of the skater's path because he is not moving at the top of his path (assuming the earth is stationary). In addition, we found that the system's kinetic energy is the greatest when the skater is at the bottom of the track because he is moving the fastest at the bottom of the track. We also found that when the skater is located somewhere between the top and the bottom of the path, the system has both gravitational potential energy and kinetic energy.
You can see similar energy transformations in lots of different systems. Look at the pendulum below, for example. Imagine the system is the pendulum and the earth. Just like the skater/Earth system in the simulation, the gravitational potential energy below is the greatest when the pendulum is at the top of its path (points A and E) and the least when the pendulum is at the bottom of its path (point C). At points B and D, the pendulum/Earth system has both gravitational potential energy and kinetic energy.
In addition, we found that the system's gravitational potential energy is greatest when the skater is at the top of his path, and we found that the gravitational potential energy is zero when the skater is at the bottom of the track (if we set the blue dotted gravitational potential energy reference marker at the bottom of the track). We found that the system's kinetic energy is zero at the top of the skater's path because he is not moving at the top of his path (assuming the earth is stationary). In addition, we found that the system's kinetic energy is the greatest when the skater is at the bottom of the track because he is moving the fastest at the bottom of the track. We also found that when the skater is located somewhere between the top and the bottom of the path, the system has both gravitational potential energy and kinetic energy.
You can see similar energy transformations in lots of different systems. Look at the pendulum below, for example. Imagine the system is the pendulum and the earth. Just like the skater/Earth system in the simulation, the gravitational potential energy below is the greatest when the pendulum is at the top of its path (points A and E) and the least when the pendulum is at the bottom of its path (point C). At points B and D, the pendulum/Earth system has both gravitational potential energy and kinetic energy.
Click HERE for another great example of the transformation of gravitational potential energy into kinetic energy.
If you would like to see a more realistic portrayal of energy transformation, make sure the skater in the Energy Skate Park simulation is still moving and select the "Track Friction >>" button. Then, drag the "Coefficient of Friction" slider to the right. If you watch the skater for a few seconds, you will see that the skater does not go as high on the track as he did before you turned friction on, and if you watch for a long enough time, he will eventually stop. In addition, if you look at the energy bar graph after turning on friction, you will see that you have been able to transform the system's gravitational potential energy and kinetic energy into a brand new form of energy called thermal energy. Thermal energy is often referred to as a "disordered form of energy," and typically, once energy has been transformed into thermal energy, it can't be easily and efficiently transformed into other more ordered forms of energy, like kinetic energy and potential energy. We will continue our discussion of thermal energy later on in the semester.
If you would like to see a more realistic portrayal of energy transformation, make sure the skater in the Energy Skate Park simulation is still moving and select the "Track Friction >>" button. Then, drag the "Coefficient of Friction" slider to the right. If you watch the skater for a few seconds, you will see that the skater does not go as high on the track as he did before you turned friction on, and if you watch for a long enough time, he will eventually stop. In addition, if you look at the energy bar graph after turning on friction, you will see that you have been able to transform the system's gravitational potential energy and kinetic energy into a brand new form of energy called thermal energy. Thermal energy is often referred to as a "disordered form of energy," and typically, once energy has been transformed into thermal energy, it can't be easily and efficiently transformed into other more ordered forms of energy, like kinetic energy and potential energy. We will continue our discussion of thermal energy later on in the semester.