Mechanical Energy

- occurs whenever an object is IN MOTION OR "WANTS" TO MOVE. It can be stored up using a spring, rubber band, or just by lifting an object higher up off the ground.

Potential (the object "wants to move")

There are three things that can change an object's mechanical potential. They are...

Mass - the more mass an object has the more potential energy it has. It takes more energy to lift something heavy.

Arnold has MUCH more mass than I do!

Arnold and Mr. Hughes are on the roof of the same building.

Who would have more potential energy?

I have MUCH less mass than Arnold!

Gravity - the pull of the Earth is what makes lifting objects difficult.

This box has less PE because it was easier to lift.

You lift a 50 lb box above your head on Jupiter and then on the moon.

Which box would have the LEAST amount of potential energy?

This box has more PE because it was harder to lift!

Height - lifting something off the ground takes energy. The higher something is lifted the more energy is being stored in the object.

The Skydiver has less PE because she is closer to the ground!

Imagine two identical twins. One is a pilot and the other is a skydiver on her way down.

Which sister has the most potential energy?

The sister in the plane is higher off the ground and has MORE PE!

The formula to calculate potential energy uses all three:

P.E. = (mass) (Gravity) (height)

 

Kinetic (the object IS moving)

 

K.E = .5 (mass) (velocity) (velocity)

Notice that velocity (like speed) has more to say about kinetic energy than the mass. It is multiplied TWICE in the equation.

I would rather have a huge truck run into me at 1 m/s...

...than have a tricycle thrown at me at 10 m/s.

But I would rather be hit by the tricycle ...

...than have a bullet shot me at 100's of m/s.

Speed REALLY impacts the kinetic energy of an object.

The bee has less mass than the eagle.

A honeybee and an eagle are both flying at 5m/s.

Which one has more Kinetic Energy?

 

The eagle has more mass than the bee.

 

 

 

 

1. Where does the roller coaster have the most potential energy?

2. Where does the roller coaster move the fastest?

3. Why is the 2nd hill shorter than the 1st?

 

 

 

ENERGY

BASICS

Chemical

Heat

Electro - magnetic

Mechanical

Nuclear

Radiant

Sound

 

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