Return to Physics IndexGive Me Energy

April Luehmann Zion Lutheran School

3840 W. 216th Street

Matteson IL 60443

(708)747-7490Objectives:

The 7th and 8th grade students will be able to define, give examples of, and

differentiate between potential and kinetic energy.Materials Needed:

per group for Lab 1

roller skate

wide, flat board (ramp)

spring scale

2 blocks of wood

some form of weight to be added to the skate

meter stick

log sheets with charts to record dataThe Lesson:

Begin by asking the students to find what the following 3 things they see have

in common.

Show them: 1. an electric cord

2. a can of Mountain Dew

3. a person climbing up a ladder

Leave the three displayed throughout the lesson. Tell themat the end of thelessonand after they have shared their hypotheses that each of the three give

something energy.Strategy:

Hypothetical Situation:

I was camping one day, and I was given the responsibility of starting the

fire. As I went out searching for fire wood, I found a terrific small log! It

was perfect with the exception that it was too long. I needed to break it.

(Bring out a thick and long piece of wood and demonstrate an attempt to brace

the wood, step on it, and show the board would not break.) Can anyone give me

suggestions as to how I can improve my potential to break my log? (List all

answers on board for later reference.)

Do LAB #1:

Directions for the student:

1. Make a ramp with a block of wood and a wide flat board. Measure the height

of the ramp. Mass a roller skate with a spring scale and record that data.

Place the skate at the top of the ramp and release it. Measure how far the

skate rolled, from the bottom of the ramp to the rear wheel of the skate.

2. Raise the ramp by adding another block under the long board. Measure and

record the new height. Repeat the process of rolling the skate and

measuring the distance it rolled. Record results.

3. Add weight to the skate. Measure and record the new mass of the skate.

Repeat the process again of rolling the skate down the ramp at each of the

two heights and measuring the distance it rolled. Record results.

4. Study the results and draw a conclusion.

*Can you give inanimate objects energy?

*Did the skate have more energy at any one time?

*How did YOU give that skate more energy?

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Return to the hypothetical situation and discuss why adding weight or height

will give you potential energy to break your "log." Discuss formula of:

gravitational Potential Energy = Weight x Height

Stand on a rung of a ladder. Ask "How can I increase my potential energy?"

Discuss other forms of potential energy: a bow and arrow with the bow pulled

back, a skydiver in an airplane, a spring compressed,...

Game: In teams of three, and in 5 minutes, come up with as many examples of

potential energy as your team can. Your team will receive one point for each

example that no other team thought of, so be creative!

"As I fall off this ladder, I lose potential energy, right? Where does it go?

What about that Law of Conservation of Energy?" Discuss and define kinetic

energy. As a class, give examples such as a book falling, water tumbling over a

water fall, a fist swinging in the air, a baseball player sliding in to home.Materials Needed:

per group for lab 2

1 full pop can

1 empty pop can

1 ramp

3 blocks of wood

3 cereal boxes or cornstarch boxes

log pages for results

Do LAB #2: BOX BOWLING

The goal of this lab is to knock over the empty cardboard boxes, i.e.accomplishWORK. (Remember work is defined as a force applied through distance.) From the

discussion of kinetic energy get the students to remind you that kinetic energy

is the energy of motion used to do work. Ask the students to try different

things to do the MOST possible work (knock over as many boxes as possible).

Rules of the lab:

1. All work must be done by a rolling can.

2. Can must be LET GO, not pushed or pulled.

3. Record every attempt you made and the data you measured.

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Finish by comparing the results of all the groups. Give them the formula for

kinetic energy:

KE = 1/2 x mass x velocity^{2}Knowing this formula, discuss which makes a greater impact on the amount of kinetic energy, increasing the mass or increasing the velocity. (Answer: increasing the velocity).Performance Assessment:

The students will receive points based on demonstrated effort, care in measuring

results and recording data, and logical and complete support for the conclusions

they claim to be true. The students will also be asked to give a VISUAL example

of both potential and kinetic energy and explain the difference between the two.