1. A large chunk of ice with a mass of 15-kg falls from a roof 8.0-m above the ground. Find the KE and the speed when it reaches the ground. What is the speed at the halfway point (@ 4 m)? Bellwork

2. Conservation of Energy

3. As long as the system is closed so that objects do not move in and out, and the system is isolated from outside forces, then energy can only change form.

4. Mechanical Energy In a system, it is the sum of KE + PE depending on the situation. Can be all KE or all PE, or a combination of both KE = 1/2 mv 2 GPE = mgh GPE is also written as U g

6. A 75-kg skier starts from rest at the top of a 45-m hill, goes down the hill, then back up a 40-m hill. Both heights are measured from the valley floor straight up. How fast was the skier moving at the bottom of the valley? What is the skier’s speed at the top of the next hill?

7. Remember the combustion engine? Heat Friction Air resistance Sound Resisting/changing motion Powering other mechanical parts

8. Kinds of Energy Mechanical – energy used to physically move things Radiant – light, radio, UV, etc. Electricity – electrical energy Heat/Thermal – energy moving from warmer to colder things Chemical – energy of making and breaking chemical bonds Nuclear – energy within the nucleus of an atom [fusion/fission] Sound – energy of sound waves

9. ChemicalKinetic PotentialRadiant NuclearSound ElectricalHeat/Thermal Construct a scenario in which at least 6 of these energies are used. Be creative! Label each energy transfer. Example: Using a photovoltaic cell (radiant to electrical) to power a fan (electrical to kinetic) that has a looped rope tied to it spinning an electrical generator (kinetic to electrical) to power a radio (electrical to sound). To be collected at the end of class.