1. Energy and Its Forms
15.1 pg

2. Energy and Work Energy is the ability to do work
Energy is transferred by a force moving an object through a distance
Work is a transfer of energy
When work is done on a n object, energy is transferred to that object

3. Example of work and energy: Carrying your backpack up stairs
Lift it -- AGAINST the force of gravity
REQUIRES energy from your MUSCLES
Muscles REQUIRE energy from FOOD
Food REQURIES energy from plants and other animals.

4. Kinetic Energy (KE) Is the energy of motion
Depends on an objects velocity (speed) and mass
The kinetic energy of any moving object depends upon its mass and speed
Kinetic Energy (KE) = 1/2 m x v2
Where m = mass in kg and v = velocity in m/s

5. Sample Problem for KE:
A 0.1 kg bird is flying at a constant speed of 8 m/s. What is the bird’s kinetic energy?
Given info:
Mass = 0.1 kg
Speed or v = 8 m/s
Step 1:
KE = 1/2 mv2
Step 2:
KE = 1/2 (0.1 kg) (8 m/s)2
Step 3:
KE = 3.2 kgm2/sec2
= 3.2 kgm/sec2 m
And because kgm/sec2 is a Newton we can write…
KE = 3.2 Nm
And Nm is a Joule
so finally…KE = 3.2 Joules

6. Potential Energy (PE)
Energy that is stored because of position or shape
A stretched string on a guitar or a streched rubber band has potential energy (PE)
Two types of PE:
Gravitational Potential Energy
Elastic Potential Energy

7. Gravitational Potential Energy(GPE)
Potential energy that depends upon an object’s height
An objects GPE depends on its mass, its height, and acceleration due to gravity
Increases when an object is raised to a higher level
GPE or PE = mgh
Where m is mass, g is gravity, and h is height

8. Sample Problem for PE
A 50 kg diver is at the top of a 10 meter high diving platform. What is the diver’s potential energy?
Given info:
Mass = 50 kg
Height = 10 m
Gravity = 9.8 m/sec2
Step 1:
PE = mgh
Step 2:
PE = 50 kg (9.8m/sec2)(10m)
Step 3:
PE = 4900 kgm/sec2 m
And because kgm/sec2 is a Newton we can write…
PE = 4900 Nm
And Nm is a Joule
so finally…PE = 4900 Joules

9. Elastic Potential Energy (EPE)
The potential energy of an object that is stretched or compressed
Examples
Stretched
Ukulele string, rubber band, etc.
Compressed
Bouncing a ball, shocks on a car, etc.

10. Forms of Energy Mechanical: Both Kinetic and Potential together
Thermal
Chemical
Electrical
Electromagnetic
Nuclear

11. Mechanical Energy (ME)
The energy associated with the motion and position of everyday objects
Sum of an objects Potential and Kinetic Energy
Does not include thermal, chemical or other forms of energy associated with the motion or arrangement of atoms or molecules
ME = PE + KE

12. Thermal Energy
Atoms in an object are always in motion
The total PE and KE of the molecules make up its thermal energy
Faster motion, more thermal energy

13. Chemical Energy
Chemical Energy is the energy stored in chemical bonds.
When broken they release energy
All chemical compounds store energy
Gives energy from food
Warm from firewood
Energy from coal

14. Electrical Energy Energy associated with electric charges
Batteries convert chemical energy into electric
Lightning bolts

15. Electromagnetic Energy
Electromagnetic energy is a form that travels through space in the form of waves
Visible light
X rays
Gamma Rays
Microwaves

16. Nuclear Energy
The energy that is stored in atomic nucleus
Nuclear power plants - fission - release energy
The sun - Fusion - release energy when nuclei combine

17. Make sure you write a summary!