1. 4.3 Conservation of Energy

2. Types of Energy – Kinetic Energy
Kinetic energy is the energy associated with motion.
KE = ½ mv2
m = mass, v = velocity

3. Types of Energy – Potential Energy
Potential Energy is stored energy:
Gravitational PE depends on:
object’s mass (m)
Acceleration due to gravity (g)
distance object could fall
PE = mgh
We next discuss 2 subcategories of potential energy that are important in astronomy: gravitational potential energy (this and next slide) and mass-energy.

4. Types of Energy – Potential Energy cont.
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.
We next discuss 2 subcategories of potential energy that are important in astronomy: gravitational potential energy (this and next slide) and mass-energy.

5. Types of Energy – Potential Energy cont.
Mass is a form of potential energy
A small amount of mass can release a great deal of energy
E = mc2

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

7. 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.
You might wish to go through the example tracing the energy of a baseball back through time, as described on p. 90 of the text.

8. Changes in Energy

9. KE & GPE for an orbiting body: