Consider the pile driver example from the last lesson. To simplify the analysis, the energy transformed to thermal energy due to friction is assumed to be zero. When the pile driver is raised, the potential energy (PE) of it increases. As it falls, the potential energy is transformed into kinetic energy (KE), because the driver increases speed as it falls to the ground.
Energy Equation
Total Energy = Kinetic Energy + Potential Energy
Total E = KE + PE
To demonstrate the law of conservation of energy, use the number 100 to represent the total amount of energy (100E) of the driver. At the highest point, all of the energy of the driver is gravitational potential energy. So the total amount of energy (E) equals 100PE. At this highest point, there is no kinetic energy because there is no movement. So KE equals zero. The law of conservation of energy can be represented by this equation: 100E = 0KE + 100PE.
When the driver is dropped, potential energy (PE) begins to transform to kinetic energy (KE). At the halfway point, half the potential energy is transformed into kinetic energy. Remember that the total energy is conserved. At the halfway point, the law of conservation of energy can be represented by this equation: 100E = 50KE + 50PE.
When the driver reaches the bottom, just as it hits the pile, it has its maximum amount of kinetic energy, 100KE. The gravitational potential energy (PE) transformed to kinetic energy (KE). The law of conservation of energy can be represented by this equation: 100E = 100KE + 0PE.
Potential Energy
When is potential energy the greatest in the pile driver?
Kinetic Energy
When is the kinetic energy the greatest in the pile driver?
