Conservation of Energy The relationship between Potential and Kinetic Energy
Relationship between KE and PE In many situations, there is a conversion between potential and kinetic energy. The total amount of potential and kinetic energy in a system is called the mechanical energy. Mechanical energy = PE + KE
Mechanical Energy Mechanical energy is due to the position and motion of the object. What happens to the mechanical energy of an apple as it falls from a tree?
Mechanical Energy As the apple falls to the ground, its height decreases. Therefore, its GPE decreases. The potential energy is not lost – it is converted into kinetic energy as the velocity of the apple increase. What happens to the mechanical energy?
Mechanical Energy The mechanical energy does not change because the loss in potential energy is simply transferred into kinetic energy. The total amount of energy remains the same. Energy is conserved and transformed. This is the Law of Conservation of Energy – energy is neither created or destroyed – the total energy is constant.
Conservation of Mechanical Energy m = mass v = velocity g = gravitational acceleration h = height Oni, did you know that even though it was a bumpy ride, our energy remained constant! Kinetic Energy Potential Energy Total Energy
Conservation of Mechanical Energy
Conservation of Mechanical Energy
Conservation of Mechanical Energy
Conservation of Mechanical Energy
Conservation of Mechanical Energy
Conservation of Mechanical Energy Is the skater above the ground? NO ; h = 0 m ; PE = 0 J Position m v KE PE E 1 60 kg 8 m/s 1920 J 0 J 1920 J
Conservation of Mechanical Energy Energy Before = Energy After E = PE + KE 1920 J = (60)(9.8)(1) + ½60v2 1920 J = 588 J + ½ 60v2 1332 J = 30v2 44.4 = v2 6.66 m/s = v Position m v KE PE E 1 60 kg 8 m/s 1920 J 0 J 2 6.66 m/s 1332 J 588 J 1920 J
Conservation of Mechanical Energy Is the skater moving at the top? NO, v = 0 m/s Energy Before = Energy After E = PE + KE 1920 J = (60)(9.8)h + 0 3.27 = h Position m v KE PE E 1 60 kg 8 m/s 1920 J 0 J 2 6.66 m/s 1332 J 588 J 3 0 m/s 0 J 1920 J 1920 J