Energy

Is all around you

Physical Science

Studying the interaction between matter and energy

Nature of Science

• You hear energy as sound, you see energy as light, you can feel energy in wind.

• Living organisms need energy for growth and movement.

• You use energy when you hit a tennis ball, lift a grocery bag, or compress a spring.

• Energy is the ability to do work and work is the transfer of energy.

Forms of Energy

• Energy appears in many forms. The following are some forms of energy:

• Mechanical• Heat• Chemical• Electrical• Sound • Light• Nuclear

Mechanical Energy

• Energy possessed by an object due to its motion or stored because of its position.

• Two types of mechanical energy:– Kinetic energy

– Potential energy

• Units Joules

Mechanical Energy

Kinetic Energy - Energy due to the motion of a body

KE = ½ mv2

Kinetic Energy (J) mass (kg)velocity (m/s)

“If you ain’t first, you’re last” claims famed race car driver Ricky Bobby. If Ricky’s 720 kg car has 4,844,000 J of kinetic energy, how fast does he go to keep in first place?

Mechanical Energy

Potential Energy - Stored energy because of relative position between interacting bodies.

PE = mgh

Potential Energy (J)mass (kg)

Acceleration due to gravity

height (m)

Potential Energy

• The Millenium Park fountain in Chicago appears to have water spitting from the mouth of a Chicago citizen. If 500 kg of water spray out of the fountain and carries 12,000 J of gravitational potential energy, how high does the water spray from?

What type of mechanical energy do the blocks have?

Potential Energy

Both Potential and Kinetic

Kinetic Energy

Law of Conservation of Energy

• Energy cannot be created nor destroyed.

• Total energy before = total energy after

• KEi + PEi = KEf + PEf