Energy Transformations Aim: To describe what happens when energy is 'used.' Keywords: Energy, Potential, Kinetic, Heat, Light "Energy can be neither created or destroyed, it transforms from one form to another." This example of a roller coaster, shows the transformation between gravitational potential energy and kinetic energy. Gravitational potential energy increases as the subject ascends above ground level. This means that when the cart is at the starting point of the roller coaster, the highest point above ground level, it contains the most amount of gravitational potential energy. Once the cart reaches the bottom of the drop, all of its gravitational potential energy has been transformed into kinetic energy. This gives the cart the momentum to reach the next hill. The cart doesn't receive any energy after the beginning, meaning that each hill has to be slightly lower than the previous, as some energy is lost to air resistance. The cart doesn't fall in the loop, because the carts kinetic motion energy is strong enough to keep the cart in forward motion, rather than fall due to gravitational energy. Finally, the cart loses all of its energy due to the opposing forces of friction and air resistance. We also learnt how to calculate energy efficiency. The formula for this, as seen in question 3 on the worksheet, is the amount of useful energy output (measured in joules,) divided by the energy input, multiplied by 100. An example of this, as seen in question 3a on the worksheet, is the toaster. For every 500J the toaster uses to run, 450J are transformed into heat energy and 50J are transformed into light energy. This can be written as (450/500)*100, (see question 3a.) This works out to be 90, meaning that the toaster has an energy efficiency of 90%. Lesson Summary
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