1. Potential Energy

2. Potential Energy examples • Give four examples of an object that has potential energy (not mentioned in the previous power point)

3. Potential energy – the energy an object or system has by virtue of its position or configuration

4. Gravitational Potential Energy (UG) • Energy stored due to an object’s position or vertical height

5. Recall… • We defined energy as an object’s ability to do work and…. • Work = Force x Displacement In order to gain potential energy due to gravity, somebody/something must put the “work” into the system • Knowing this, we can transform the Work equation into one for gravitational potential energy

6. UG Equation • Work = Force x Displacement • The force that must be overcome is due to gravity, therefore, Force = mass x gravity. • When changing an object’s vertical position, you cause a displacement…and we’ll just call that h, for height • Now…. • Work = (mass x gravity) x height • Once the work has been put into the system, it turns into energy…therefore • UG= mgh

7. Calculating UG • Calculate the UG contained by an Will I. Flye (80 kg), jumping from a height of 1800 meters. • Will’s friend, May B. Knot, has a smaller mass (65 kg), but jumps from 1900 meters. Who has more UG?

8. Energy Transfer Will and May land…how much UG do they contain now? • Knowing energy cannot be created or destroyed, where did the energy go?

9. Energy Transfer • The answer lies in energy’s ability to transform into other forms. • Will I. Flye and May B. Knot had UG to begin with, but were not moving. • After jumping off the cliff, explain what happens? • They start accelerating towards the ground • Their height decreases • They transferred UG into kinetic energy, K (moving energy)

10. Other examples of UG transfers into K • Write down an example of another transfer similar to this one

11. Recalling an earlier picture… • Why does Katniss have potential energy? • Is this UG? • This is called elastic potential energy, Us

12. Elastic Potential Energy, Us • Scalar • Measured in Joules, J • the energy stored in elastic materials as the result of their stretching or compressing

13. Meet Mudd… • http://www.youtube.com/watch?v=tU9RSNXaElw

14. Elastic Potential Gone Wrong • http://youtu.be/usOfHcu-YII?t=20s

15. Calculations using Us • Us=1/2kx2 • k = spring constant • Measures how “stiff” the spring is. • Higher the k, the stiffer the spring • Units are N/m • x = displacement from equilibrium position • Mudd, the jumping bulldog, has a mass of 25 kg, the trampoline has spring constant of 25,000 N/m, and he compresses it 0.1 meters. • How much Us does the trampoline contain?

16. Other examples of energy transfers… • http://youtu.be/ALdXhl7zveY?t=50s • http://youtu.be/F92FQdnLlSc?t=39s