Energy Transformations

• Several forms of energy have been defined.

• Each kind can be changed into other kinds

Forms of EnergyPotential: Stored Energy Kinetic: Energy of Motion

Chemical Energy Electrical Energy

Nuclear Energy Radiant Energy

Gravitational Energy Sound Energy

Stored Mechanical Energy Mechanical Energy

Thermal Energy

Chemical Energy• energy stored in bonds that hold atoms

together as molecules.

Food

Fuel

Nuclear Energy• energy stored in the nucleus of an atom;

released when nuclei split apart or join together

Nuclear FissionNuclear Fusion

Nuclear Power Plants Fusion in the sun

Gravitational Energy

• energy stored in an object as the result of its height

Roller coaster car at top of hill

Pendulum

Elastic Potential Energy• energy stored in elastic materials as the result

of their stretching or compressing.

Stretched Rubber Band

Compressed spring

Electrical Energy

Lightning

Energy of moving electrical charges

Electrical charges moving through wire

Radiant Energy

• Energy that travels as electromagnetic waves.

Xrays

Microwaves

“David Banner belted by gamma rays turns into The Hulk”

Sound Energy

• Energy given off by vibrating objects; energy we can hear

Mechanical Energy

• Energy of motion used to do work

Flowing water

Wind

Your body when you move

Machines

Thermal Energy• Thermal energy is the energy an object has

due to the motion of its molecules. The faster the molecules in an object move, the more thermal energy the object has.

The lava flowing from this volcano has a large amountof thermal energy.

Calculating Gravitational Potential Energy

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?

Calculating Gravitational Potential Energy

An apple with a mass of 0.1 kg is attached to a branch of an apple tree 4 m from the ground. How much gravitational potential energy does the apple have?

Calculating Gravitational Potential Energy

If you lift a 2 kg box of toys to the top shelf of a closet, which is 3 m high, how much gravitational potential energy will the box of toys have?

Calculating Kinetic Energy

• What is the kinetic energy of a girl who has a mass of 40 kg and a velocity of 3 m/s2?

Calculating Kinetic Energy

• A grasshopper with a mass of 0.002 kg jumps up at a speed of 15 m/s. What is the kinetic energy of the grasshopper?

Calculating Kinetic Energy

• A truck with a mass of 6000 kg is traveling north on a highway at a speed of 17 m/s. A car with a mass of 2000 kg is traveling south on the same highway with a speed of 30 m/s. Which vehicle has more kinetic energy?

Mechanical Energy

• A satellite falling to Earth has a kinetic energy of 182.2 billion J and a potential energy of 1.6 billion J. What is its mechanical energy?

Mechanical Energy

• If the kinetic energy of a falling apple is 5.2 J and its potential energy is 3.5 J, what is its mechanical energy?

Energy Transformations

• Energy can be changed, or transformed, from one form to another.

Mechanical Energy Electrical Energy

Mechanical energy of moving water can be transformed into electrical energy

Electrical Energy Thermal Energy

• A toaster transforms electrical energy into thermal energy to toast your bread

Chemical Energy Mechanical Energy

• Your body transforms the chemical energy in your food to mechanical energy you need to move your muscles.

Chemical Energy Thermal Energy

• Chemical energy in food is also transformed to the thermal energy your body uses to maintain temperature.

Energy Transformations

Many common devices transform electrical energy into other forms. Thinks about the following devices in terms of energy transformations.ceiling fan digital clock hair dryerFor each device, describe which form or forms of energy the electrical energy becomes.

Radiant Energy Chemical Energy

• Green plants change radiant energy (light) to chemical energy.

Chemical Energy Mechanical Energy

• Burning fuels changes chemical energy into mechanical energy

Electrical Energy Light Energy

• A lightbulb changes electrical energy to light energy

Conservation of Energy• In any energy transformation, some energy

changes to heat.• Energy can be changed from one form to

another but it can never be created or destroyed.

• A sliding hockey puck comes to rest because friction converts its kinetic energy into heat.

Energy and Friction

Energy and Matter