EQ – How is life affected by energy? S8CS2 (Habits of Mind) & S8CS8 (Nature of Science) S8P2. Students will be familiar with the forms and transformations of energy. a. Explain energy transformation in terms of the Law of Conservation of Energy. b. Explain the relationship between potential and kinetic energy. c. Compare and contrast the different forms of energy (heat, light, electricity, mechanical motion, sound) and their characteristics. d. Describe how heat can be transferred through matter by the collisions of atoms (conduction) or through space (radiation). In a liquid or gas, currents will facilitate the transfer of heat (convection).

Energy Energy is the ability to do work.

Kinetic energy -the energy of motion. KE depends on both mass and speed. The more mass an object has the more kinetic energy it has. The faster something is moving, the more kinetic energy it has.

Changing the velocity (the speed in a specific direction) of an object will have a greater effect than changing its mass. Why? (KE= ½ x M x V²)

Speed has a greater effect on kinetic energy than mass does. Why? KE= ½ x M x V² M= mass V = speed

Calculate What is the kinetic energy of a girl who has a mass of 40 kg and a velocity of 3 m/s? What do you know: mass = 40 kg, velocity = 3 m/s Write the formula: KE = ½ mv 2

Substitute into the formula: KE = ½ x 40 kg x (3 m/s) 2 KE = ½ x 40 kg x 9 m 2 /s 2 = 360 kg x m 2 / 2 s 2 = 180 kg x m 2 /s 2 Or KE = 180 J

Solving Velocity Velocity = distance/time Example: V= 50m/32s = 1.56 m/s

A hockey player on the ice has kinetic energy

-stored energy. The ball has Potential to move.

Potential energy can be increased by: Increasing height Increasing mass

Three Types of Potential Energy Elastic – energy stored in objects that can be stretched Chemical – energy stored within chemical substances (i.e. coal) Gravitational – energy due to the height of an object (PE= M x 9.8 m/s/s [acceleration due to gravity] x height)

Calculating PE PE = mgh where PE = Energy (in Joules) m = mass (in kilograms) g = gravitational acceleration of the earth (9.8 m/sec 2 ) h = height above earth's surface (in meters)

What is the gravitational potential energy of a girl who has a mass of 40 kg and is standing on the edge of a diving board that is 5 m above the water?

What do you know? –Mass = 40 kg, gravitational acceleration = 9.8 m/s 2, height = 5 m What do you want to find out? GPE Write the formula: GPE = mph Substitute into the formula: 40 kg x 9.8m/s 2 x 5 m

GPE = 1960 kg m 2 /s 2 Unit of energy is Joules or J Answer: 1960 J

A rubber band has potential to be shot. (elastic energy)

What other things can you think of that have potential energy?

A waterfall has both kinetic and potential energy.

The water at the top of the waterfall has stored potential energy.

Once the water leaves the top of the waterfall, the potential energy is changed into kinetic energy.

Law of Conservation of Energy Energy cannot be created or destroyed; it may be changed from one form to another, but the total amount of energy never changes.

Forms of Energy Chemical – holds atoms and molecules together; released by chemical reactions Electrical – movement of electrons through matter; electricity Heat – vibration of particles within matter; faster = more heat Light/Radiant – energy carried by light; electromagnetic spectrum Mechanical – energy of moving things Sound – vibration of air molecules that causes movement of tiny bones in your ear to send a message to your brain in order for you to hear; vibrates all forms of matter Nuclear – holds protons and neutrons together in the nuclei of atoms; powers the sun and nuclear power plants More info:

Just Remember Mrs. Chen Mechanical Radiant Sound Chemical Heat Electrical Nuclear