TOPIC Energy AIM Describe potential and kinetic energy
TOPIC: Energy AIM: Describe potential and kinetic energy and conversions that can occur between these two forms of energy. Do Now: Take out HW ditto Top of the Ditto on the back of yesterday’s notes. HW: Bottom of Physical and Chemical Properties Review Ditto Chemistry Castle Learning due on Tuesday!
Energy • Ability to do work • Unit = JOULES (J)
Law of Conservation of Energy • Energy cannot be created or destroyed, only changed from one form to another
Think of energy as money. $100 can be saved in many forms… Cash in your wallet, a bank account, travelers’ checks, gold or silver coins… Money can be transferred to different forms. It can be deposited in a bank account, or traded for gold. No matter what form, money is money… The same is true for energy. Energy from the sun and energy from food are only different forms of the same thing.
Kinetic Energy • Energy of motion
What can cause an • Increase in velocity increase (speed) in KE? • Larger mass
Potential • Stored energy Energy • Object is not moving
Examples 1. Stretched rubber of PE band = a lot of PE – Let it go PE is released
2. Unlit match = PE stored till lit
The massive ball of a demolition machine and the stretched bow possess stored energy of position = Potential Energy
The heavy ram of a pile driver and the stretched bow possess stored energy of position = POTENTIAL ENERGY.
Gravitational • PE that depends on height PE • More height greater GPE • Less height less GPE
• Example: Person on a 3 m diving board has more GPE than person on 1 m board
• Change of energy from Energy 1 form to another Conversion • KE PE • PE KE
As the car loses height, it gains speed. PE is changed into KE. The sum of the KE and PE is constant. It never changes.
REVIEW: KINETIC OR POTENTIAL ENRGY?
The ram of a pile driver has mechanical energy When held up, it has mechanical energy in the form of potential energy. As it falls, it has mechanical energy in the form of kinetic energy. As it strikes the spike, it applies a force to move the spike (it does work on it).
On the platform: KE = 0 J PE = max During the jump: KE is increasing PE is decreasing PE KE In the water: KE = 0 J PE = max
Let’s summarize… 1. What is energy. How is it measured? 2. Describe the Law of Conservation of Energy. 3. Explain the difference between kinetic energy and potential energy. 4. What can cause an increase in kinetic energy? 5. Describe the relationship between height and gravitational potential energy. 6. Describe the following energy conversions: - jumping off a diving board - throwing a ball into the air
A high diver steps off a diving platform that is 10 m above the water. If no air resistance is present, during the fall there will be a decrease in the diver’s 1. gravitational potential energy 2. total mechanical energy 3. kinetic energy 4. momentum
Which of the following is an example of kinetic energy? 1. A car not moving 2. Water falling off a dam 3. A rock resting on a ledge 4. A person sitting in a chair
Which of the following increases when a metal spring is stretched horizontally? 1. Potential energy 2. Kinetic energy 3. Gravitational potential energy 4. Electrical energy
What happens to the kinetic energy and gravitational potential energy of a ball during free fall? 1. GPE and KE both increase. 2. GPE and KE both decrease. 3. GPE decreases and KE increases. 4. GPE increases and KE decreases.
• If both of these balls are traveling down a bowling lane at the SAME speed, which one would have more kinetic energy? Support your answer.
Which skier will have a greater potential energy? Support your answer.
At which two points on the pendulum, is the pendulum experiencing the greatest potential energy?
- Slides: 32
