ENERGY & ENERGY & POWERPOWER

I. Energy = the ability to do work.

A. Work and Energy:are related, we give energy to an object by doing work on the object.

B. Measuring Energy: Because work is the transfer of energy, we can measure energy by measuring the work done.

For example if a boat does 5,000 Newton’s of work, the engine of the boat put out 5,000 N-m’s of energy.

One Newton meter is = to a Joule (J)

So to find out how much energy is needed to do something we use the formula for work.

II.Kinetic Energy: is the energy of motion.

A. If you stop a moving object you can feel it’s Kinetic Energy.

1. Kinetic Energy depends on two things.

Mass & Speed of the object.

100km/hr

100km/hr

More Kinetic Energy

III.Calculating Kinetic Energy:

KE=1/2mv2 answer is in Joules.

mass velocity

Example: A girl has a mass of 40 kg skates around a rink at 12m/s. What is her Kinetic energy?

1.A boy has a mass of 120 kg runs at a speed of 4 m/s. What is his KE?

2.A man has a mass of 100 kg walks at a speed of 2 m/s. What is his KE?

3. A baseball with a mass of 0.08 kg is thrown at a speed of 20 m/s. What is the KE of the baseball?

4. A soccer ball with a mass of 2 kg is kicked at a speed of 5 m/s. What is the KE of the soccer ball?

IV.Potential Energy: Is energy due to an objects position.

A. Calculating Potential Energy: Is work done or Force X Distance = Joules

1. Example: If a boy carries a 70 n bowling ball up a flight of 20 m high stairs. What is the balling ball PE?

Answer: 70 n X 20 m = 1400 J

B.Law of Conservation of Energy: States that energy cannot be created or destroyed. It can change from one form to another. But the total amount of energy remains the same. {EXCEPT SOME IS LOST DUE TO FRICTION}

C.Friction Wastes Energy:

1. The lower the friction the less energy wasted.

2. The less energy wasted the faster you go.

3. The less energy wasted the more PE converted to KE.

PE

PE & KE

PE if

Stopped

V.V.Forms of EnergyForms of Energy1.Mechanical: energy an object has

from its motion.

2.Internal: energy from all the particles of an object.

3.Electrical: electricity

4. Chemical: energy from an objects position and its form of PE.

5. Radiant: energy in the form of a wave the sun

6. Nuclear: energy released from splitting or combining atoms.

A.Power: is the rate at which work is done.

1. Power = work/time it’s the rate at which energy is used.

Example: If a person used 1200 J’s of energy in 10 minutes how much power does that person have?

Answer: 1200 J / 10 minutes = 120 J/m

Some times we convert minutes to seconds for example 10 minutes = 600 seconds.10 X 60.

2. 1 Joule per second is equal to a watt (W)

3. Power is measured in watts.

1- 1- ChemicalChemical EnergyEnergy: : Energy from an objects position. (Potential Energy)2- 2- ElectricalElectrical EnergyEnergy: : Energy that flows through a wire (Kinetic Energy)3- 3- EnergyEnergy: : The ability to do work.4- 4- InternalInternal EnergyEnergy: : Energy to the particles that make it up.5- 5- JouleJoule: : Metric Unit for energy.

6- 6- KineticKinetic EnergyEnergy: : Energy because the object is moving.7-7- LawLaw ofof ConservationConservation ofof EnergyEnergy: Energy cannot be created or destroyed. Energy changes from on form to another.8- 8- MechanicalMechanical EnergyEnergy: : Energy an object has from its motion. 9- 9- NuclearNuclear EnergyEnergy: : Form of Potential Form of Potential energy the splitting of atomsenergy the splitting of atoms

10- 10- PotentialPotential EnergyEnergy: Energy due to an objects position. We give objects energy by doing work on them. 11- 11- PowerPower: : The rate at which work is done. 12- 12- RadiantRadiant EnergyEnergy: : Energy from the sun in the form of a wave. 13- 13- WattWatt: : Metric unit for power.

A

B

C

5 N14-If the rock's potential energy is100 J, the hill is _________ high.

15-At point C, the rock's potential

energy will be __________ .

16-The rock's kinetic energy at point

A is __________.

17-At point B, some of the rock's potential energy will be changed to. ________________________________

18-The rock's potential energy at point A is __________ than it's kinetic energy.