Unit 5 Relationships among forms of energy 8th Grade Middle School science Union township school district

Energy Two types of energy: Kinetic Energy Potential Energy The ability of a system to do work. Two types of energy: Kinetic Energy Potential Energy

All forms of energy can be in either of two states: KINETIC ENERGY POTENTIAL ENERGY

What’s the difference? Kinetic Energy is the energy of MOTION Potential Energy is STORED energy due to an objects position.

Kinetic Energy – what does it depend on? The faster an object moves (velocity) , the more kinetic energy it has. The greater the mass of a moving object, the more kinetic energy it has. Kinetic energy depends on both mass and velocity.

Some types of kinetic energy include… Electrical - The energy that an electric current carries is a form of kinetic energy. Radiant - the energy carried by electromagnetic waves. Sound - energy carried by sound waves Seismic - is the energy transferred by waves moving through the ground.

Calculating Kinetic Energy What has a greater affect of kinetic energy, mass or velocity? Why?

What is the unit for Kinetic Energy? Unit: Joule Named after: James Prescott Joule He discovered the relationship between heat (energy) and mechanical work which led to the law of conservation of energy. How do we derive this unit? 1 Joule = 1kg ∙ m2/s2 KE = ½ ∙ m(kg) ∙ v(m/s) 2

Practice Problem 1 What is the Kinetic Energy of a 150 kg object that is moving with a velocity of 15 m/s?

Practice Problem 2 What is the Kinetic Energy of a 1200 kg object that is moving with a velocity of 24 m/s?

Practice Problem 3 What is the Kinetic Energy of a 478 kg object that is moving with a velocity of 15 m/s?

Practice What is the Kinetic Energy of a 150 kg object that is moving with a speed of 15 m/s?   An object has a kinetic energy of 25 J and a mass of 34 kg, how fast is the object moving? An object moving with a speed of 35 m/s and has a kinetic energy of 1500 J, what is the mass of the object.

Potential Energy Stored energy that depends on the interaction of objects, particles, or atoms.

Some types of Potential Energy include… Gravitational potential energy Elastic potential energy – - stored energy due to an objects position (height) - depends on mass of the object and its distance from earth. - Stored energy due to compression or expansion of an elastic object

Some types of Potential Energy include… Chemical energy - energy that is stored in and released from the bonds between atoms. Nuclear– energy stored in and released from the nucleus of an atom.

Calculating Potential Energy If you are given Newton’s (N) that is the product of mass and gravity. A Newton is a force Gravity (acceleration due to gravity) = 9.8m/s2 on Earth.

What unit do we use for Potential Energy? Unit: Joule How do we derive this unit? 1 Joule = 1kg ∙ m2/s2 PE = m(kg) ∙ g (m/s2 ) ∙ height (m)

1. You serve a volleyball with a mass of 2. 1 kg 1. You serve a volleyball with a mass of 2.1 kg. The ball leaves your hand with a speed of 30 m/s. The ball has ___________ energy. Calculate it.

2. A baby carriage is sitting at the top of a hill that is 21 m high 2. A baby carriage is sitting at the top of a hill that is 21 m high. The carriage with the baby weighs 12 N. The carriage has ____________ energy. Calculate it.

3. A car is traveling with a velocity of 40 m/s and has a mass of 1120 kg. The car has ___________energy. Calculate it.

4. A cinder block is sitting on a platform 20 m high 4. A cinder block is sitting on a platform 20 m high. It has a mass of 5kg. The block has _____________ energy. Calculate it.

5. A roller coaster is at the top of a 72 m hill and weighs 966 N   5. A roller coaster is at the top of a 72 m hill and weighs 966 N. The coaster (at this moment) has ____________ energy. Calculate it.

6. Two objects were lifted by a machine 6. Two objects were lifted by a machine. One object had a mass of 2 kilograms, and was lifted at a speed of 2 m/sec. The other had a mass of 4 kilograms and was lifted at a rate of 3 m/sec. a. Which object had more kinetic energy while it was being lifted?  b. Which object had more potential energy when it was lifted to a distance of 10 meters? Show your calculation.

A combination of Kinetic and Potential Energy Thermal - The sum of the kinetic energy and potential energy of the particles that make up an object The motion of the particles PLUS the distance between the particles. Mechanical - The sum of potential energy and kinetic energy in a system of objects. The motion of the object PLUS the objects position

As a basketball player throws the ball into the air, various energy conversions take place.

Law of Conservation of Energy Energy can be neither created nor destroyed by ordinary means. Energy can be from one form to another. The total amount of is the before and after any transformation or transfer. transformed or transferred energy same

Energy Transfer Energy TRANSFER is the passing of energy from one object to another object. Example: A cup of hot tea has thermal energy. Some of this thermal energy is transferred to the particles in cold milk, in which you put to make the coffee cooler.

Energy Transformation A change from one form of energy to another.

Energy Transformation An objects energy can be: As velocity kinetic energy and potential energy As velocity kinetic energy and potential energy 1. All Kinetic Energy 2. All Potential Energy 3. A combination of both increases increases decreases decreases decreases increases INVERSE WHAT IS THE TYPE OF RELATIONSHIP KE AND PE HAVE?

Identify the following: Greatest Potential Greatest Kinetic Least Potential Least Kinetic Area where both kinetic and potential energy is almost even.