NATURE OF ENERGY

CATAPULT DESIGN/MOUSE TRAP COMPETITION

I. What is Energy??

A. Energy Basics1. Energy can be defined as the ability to do work.

a. An example of work would be an object/organism exerting a force over a distance to move an a object….therefore the object uses energy.

b. Electric charges in a current use energy as they move along a wire(we discussed this!!!)

c. Energy can be measured in joules (J)… which is the same unit used to measure work.

2. In addition to objects using energy to do work, objects can energy because work is being done on them.

a. If work is done an object, energy is given to that object.

b. If you fling a ping pong ball with a mousetrap…you give the ping pong ball energy to make it move.

II. Forms of Energy

A. Five main forms of Energy1. Mechanical2. Heat3. Chemical4. Electromagnetic5. Nuclear

B. Mechanical Energy1. Energy associated with motion is called

mechanical energy. a. Water in a waterfall has great mechanical energy!!!b. Other examples include wind, automobiles, walking,

swimming, blood flowing through your veins and LAUNCHING PING PONG BALLS from a mousetrap!!!

c. **Sound is also a type of mechanical energy…sound waves move mechanically!!

C. HEAT ENERGY1. Internal motion of ATOMS is called heat energy.

a. All matter is made up of atoms that are constantly moving.

2. The faster the particles move…the more heat energy is produced.a. Using the friction between your hands….when you rub your

hands together…you take the mechanical energy (movement of hands) and convert it into heat energy.

3. Heat energy usually results from friction. 4. Heat energy causes changes in temperature and may

cause change in phase (solid to liquid, liquid to gas..etc. )

D. Chemical Energy (Think Bombs!!)1. Energy exists in the bonds that hold atoms together. 2. This energy is called chemical energy.3. When bonds are broken this energy is released. 4. When fuel is burned, chemical energy is released

and converted into heat energy. 5. Digestion of food is another example of chemical

energy6. When you exercise (mechanical Energy) your body

needs the chemical energy stored in your muscles.

E. Electromagnetic Energy1. Power lines carry electromagnetic energy into

our homes in the form of electricity. 2. Each color in visible light (ROYGBIV) is

electromagnetic energy. a. Each color represents a different amount of energy.

3. X-Rays, Microwaves, Infra-red, ultraviolet, and Gamma Rays are also examples.

F. Nuclear Energy1. The nucleus or center of the atom contains NUCLEAR

ENERGY. 2. When the nucleus splits, nuclear energy is released in

the form of heat and light energy. a. This is called fission and is the main principal of nuclear

reactors.

3. Nuclear energy is also released then lightweight nuclei collide at high speeds and fuse (join). a. This is like the forming of the sun and called fusion. b. We cannot duplicate fusion.

QEUSTIONS YOU WILL NEED TO KNOW!

1. What is energy?2. Can energy be transferred from one object to

another? Explain (give examples)3. What are the different forms of energy?4. Why is energy measured in the same unit as

work?

II. Kinetic Energy and Potential Energy

1. Two STATES of energy are potential and kinetic.

a. Our example will be a set mouse trap (or catapult).

b. If you take your finger and hold the mousetrap back without setting it….even though the mouse trap is not moving there is a form of energy at rest keeping that mousetrap in that position……

2. Kinetic Energya. The energy of motion is called kinetic energb. Because the object is in motion it has the ability

to do work….hence the term energy. c. Kinetic comes form the Greek root for movement. d. The faster an object moves the more kinetic

energy it has. e. If the same person is runs for 2 miles, then crawls

for 2 miles…when do they have the most kinetic energy?

3. Do all objects have the same kinetic energy?a. Kinetic energy depends upon the mass and the

velocity (speed with direction). b. The mathematic relationship between kinetic energy

(K.E.), mass, and velocity is:

c. According to this equation, an increase in either mass or velocity will mean an increase in kinetic energy.

d. Which of these factors will have a greater affect on kinetic energy?? Why???

4. POTENTIAL Energya. Potential energy is the energy of position, or

energy at rest. b. The mousetrap that is set…but not moving has

zero kinetic energy…but it does have potential energy.

c. The chemical energy stored in food is also considered potential energy….give two more examples!!!

5. Gravitational Potential Energya. Potential energy that is dependent on height is

called gravitational potential energy. i. Waterfalls, suspension bridges, even a mouse trap

raised to a different height and snowflakes have gravitational potential energy.

b. Weight also determines the amount of gravitational potential energy an object has.

i. “The bigger they are, the harder they fall” is an observation of the effect of weight on gravitational potential energy.

6. How to determine Gravitational Potential Energy

a. The relationship between gravitational potential energy (G.P.E.), weight, and height can be expressed in the following formula:

b. The greater the weight the greater the GPEc. The greater the position above the surface, the

greater the GPE.

1. What is kinetic energy? Potential Energy?a. Energy of motion, energy of position.

2. Use the formula for kinetic energy to describe the relationship between the kinetic energy of an object, its mass, and its velocity.

a. KE is equal to ½ the product of mass times square of velocity.

3. What is gravitational potential energy? How is it calculated?

a. Potential energy due to height above ground; PE equals weight times height.

III. Energy Conversions

A. Kinetic-Potential Energy Conversions1. One of the most common energy conversions involves the

changing of potential energy to kinetic energy or kinetic to potential.

2. Throwing a ball from rest up into the air is a great example. a. Ball has all potential at the start. b. You give it kinetic energy. c. As the ball rises is slows down, so its kinetic decreases and

potential increases. (because it height increases)d. At the top the ball is stopped!!! It now only has potential energy. e. As the ball falls it speeds up, loses potential and gains kinetic.

B. Other conversions1. All forms of energy can be converted to other

forms. a. Solar energy can be used as heat energy, light energy,

chemical energy (photosynthesis),and converted into electricity.

b. Electric motors: electromagnetic energy is converted to mechanical energy.

c. Battery: chemical energy is converted to electromagnetic energy.

III. Things to know!!!

1. Describe the conversions between potential and kinetic energy as a tennis ball drops, hits the ground, and bounces back up.

a. Before the ball drops all of its energy is potential. As it falls, potential energy is converted into kinetic energy. When it hits the ground its kinetic energy is at the maximum. Then as it bounces back up, kinetic energy is converted into potential.

III. Things to know!!!

2. What energy conversions take place in a pendulum? Why does the pendulum eventually stop?

a. A pendulum converts potential energy into kinetic energy as it swings down, and kinetic energy into potential energy as it swings up. As it swings, it loses energy to friction caused by the particles of air and by the apparatus holding the top of the pendulum. Thus, it eventually slows down and stops.

III. Things to know!!!

3. Describe the energy conversions that you think take place when a flashlight is turned on.

a. Chemical energy in the batteries is converted into electromagnetic energy in the form of a current. The current is then converted into light.

IV. Conservation of Energy

A. Law of Conservation of Energy1. Energy can be neither created nor destroyed by

ordinary means. 2. Energy can only be converted from one form to

another. 3. Energy is never lost, even when one form of

energy is converted to another.

B. Albert Einstein 1. 1905: According to Einstein even the tiniest

mass can form a tremendous amount of energy. 2. Einstein’s theory of relativity deals with the

concept that mass and energy are DIRECTLY related.

3. Einstein believes that mass and energy can be converted into each other. (deep….really deep thoughts!!)

B. Albert Einstein4. With this relationship Einstein clarified the LAW of

conservation of energy. 5. He showed that if matter is destroyed, energy is

created and if energy is destroyed, matter is created. 6. The total amount of mass and energy is conserved7. Mass is continuously changed to energy in our SUN

through a process called nuclear fusion. a. During fusion a small loss in mass produces a HUGE

amount of energy!!!

Think about this……

1. What is the law of conservation of energy?a. Energy can neither be created or destroyed by

ordinary means.

2. How does the law of conservation of energy relate to energy conversions?

a. Energy conversions involve changes in the forms of energy. They occur without the loss or gain of energy.

Think about this……

3. Using the law of conservation of energy…..Explain why you become pushing a shopping cart 3 miles?

a. Energy is neither created nor destroyed, you must be giving your energy to the cart. As you give up your energy (both chemical and mechanical) your muscles become tired.