1. BC Science Connections 10 Topic 3.4: Conservation of Energy

2. Law of Conservation of Energy
Within an isolated system, energy can change form. However, the total amount of energy is constant.
Energy is neither created nor destroyed.
Energy only transforms into other forms of energy (thermal, elastic, electric potential, gravitational potential, etc.)

3. We observe this law in our lives:
A car’s hand brake fails at the top of a hill and the car begins to roll down towards a busy intersection.
A stuntman jumps out of a window of a building and onto a large air mattress.

4. Imagine a 0.50 kg ball is held 2.0 m off the ground and then dropped.
Example 1
Imagine a 0.50 kg ball is held 2.0 m off the ground and then dropped.
Position A
The ball has yet to be released and has a potential energy of:

5. The ball has been released and has a potential energy of:
Example 1
Position B
The ball has been released and has a potential energy of:
What happened to remainder of the energy?
Why is some energy missing?

6. Example 1
Position C
The ball no longer has any PE because, right before it hits the ground, all of the PE has been transformed into KE.

7. In the previous example, we can see that the decrease in PE results in an equal increase in KE.
Thus, the sum of PE and KE is always constant in an isolated system.
KEi + PEi = KEf + PEf
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