Potential Energy

Wile E. Coyote & Roadrunner Clip

Gravitational Potential Energy

GPE = mghm=massg=gravity (9.8 m/s2)h=height above a surface

AAK! A Formula!The letters are variables and

they’re placeholders for actual numbers.

Because the letters are side-by-side, you multiply them together.

To figure out potential energy, put numbers for all three and multiply together.

What units do I use?Mass is measured in…

–KilogramsGravity is measured in…

–Meters/Second2

Height is measured in…–Meters

kg x m x m =

s2

kg•m2 = Joules

s2

Let’s Try Some EquationsPE = mghFor example, plug in 4

kilograms for m and 6 meters for h (ALWAYS use 9.8 m/s2 for g)

What’s the potential energy?–(4kg)(9.8 m/s2 )(6m)–235 joules (approximately)

What if you double or triple the 4kg to 8kg or 12kg?

What if you double or triple the 6m to 12m or 18m?

Do the results agree with our experiment?

3m

1m

2m

2kg

3kg

1kg

1kg

What if you are given energy?A bowling ball dropped from a

height of 6 meters has 294 Joules of energy. What is the bowling ball’s mass?

What do we Know?–h = 6 meters–g = 9.8 m/s2

–PE = 294 JPE = mgh294 J = (m)(9.8)(6)

294/58.8 = m

5 = m

Calculating Potential Energy

Mary is painting the ceiling in her bedroom. If her mass is 55 kg and she stands on a stepladder 1 meter high, how much potential energy does she have?

m = 55kg h = 1 m g = 9.8 m/s2

PE = 55 x 1 x 9.8 PE = 539 Joules

Calculating Potential Energy

The Drop Zone at King’s Island has a maximum weight limit of 2000kg and transfers 1,960,000 Joules of potential energy into kinetic to give riders a big thrill. How high does the Drop Zone go?

m = 2000 kg PE = 1,960,000 J g = 9.8 m/s2

1,960,000 = 2000 x h x 9.8 h = 100 meters

Now YOU try! Which team can come up with the

funniest scenario for potential energy? What you need to include:

– 1. A paragraph “story”– 2. The mass of the object in kg– 3. The height of the object in meters– 4. An illustration of the scenario and– 5. Your work at the bottom that correctly

solves the problem and included the energy in JOULES.