1. 4.3 Energy and Conservation Laws

2. Kinetic energy is the energy associated with motion. KE = ½ mv 2 m = mass, v = velocity Types of Energy – Kinetic Energy

3. Potential Energy is stored energy: Gravitational PE depends on: –object’s mass (m) –Acceleration due to gravity (g) –distance object could fall –PE = mgh Types of Energy – Potential Energy

4. PE In space, an object or gas cloud has more PE when it is spread out than when it contracts.  A contracting cloud converts gravitational potential energy to thermal energy.

5. Mass is a form of potential energy A small amount of mass can release a great deal of energy E = mc 2

6. Radiative Energy – energy from light Types of Energy – Radiative Energy

8. Conservation of Energy Energy can’t be created or destroyed. It can change form or be exchanged between objects. The total energy content of the Universe was determined in the Big Bang and remains the same today.

9. KE & GPE for an orbiting body:

10. Momentum Momentum: a property of moving objects Momentum = mass  velocity A net force changes the momentum of an object

11. Conservation of Momentum The total momentum of a system can’t change unless an external force is applied Interacting objects exchange momentum through equal and opposite forces

12. Spinning or orbiting objects have angular momentum Angular momentum = mass x velocity x radius L = m v r

13. m x v x R= m x V x r Conservation of (angular) momentum: the angular momentum of an object can’t change unless an external twisting force is applied This explains why objects rotate faster as they shrink in radius:

14. For an orbiting body, this means if r is small, v is big and if r is big, v is small