Jump!Jump!

An elastic potential to kinetic An elastic potential to kinetic energy investigation.energy investigation.

Also known as “Can Paper Frogs Also known as “Can Paper Frogs Do Work?Do Work?

Elastic Potential EnergyElastic Potential Energy

Elastic potential energy can be created when a Elastic potential energy can be created when a spring (or a rubber band) is either stretched or spring (or a rubber band) is either stretched or compressed.compressed.

Basically, you change the shape of an object Basically, you change the shape of an object (you do work on the object) to deform it.(you do work on the object) to deform it.

As long as you hold the object in its deformed As long as you hold the object in its deformed shape, it will have the potential to do work – in shape, it will have the potential to do work – in other words, if you let go it will move and other words, if you let go it will move and release the energy you put into it.release the energy you put into it.

Energy (calculated) = Work (calculated)Energy (calculated) = Work (calculated)

Energy is defined as the ability to do work Energy is defined as the ability to do work or cause the change in the speed, direction, or cause the change in the speed, direction, shape, or temperature of an objectshape, or temperature of an object. .

Work is done when a force causes an object to Work is done when a force causes an object to move.move.

There is a very close relationship between There is a very close relationship between work and energy. Both work and energy are work and energy. Both work and energy are measured in Joules.measured in Joules.

Huh?Huh?

OK, check out Mrs. D - holding a large rubber OK, check out Mrs. D - holding a large rubber band.band.

The rubber band is stretched – it’s shape is The rubber band is stretched – it’s shape is changed.changed.

If she suddenly let go of the rubber band it If she suddenly let go of the rubber band it would go into motion – it would have Kinetic would go into motion – it would have Kinetic energy…energy…

……and we already know objects with kinetic and we already know objects with kinetic energy can do work.energy can do work.

Jumping FrogsJumping Frogs

Make a jumping frog the way it is shown in the video Make a jumping frog the way it is shown in the video and outlined in the handout.and outlined in the handout.

How does the frog move? Why does it move? How does the frog move? Why does it move?

Is this compression or stretching?Is this compression or stretching?

Try different angles and different amounts of pressure Try different angles and different amounts of pressure to see if you can control the way the frog jumps.to see if you can control the way the frog jumps.

Try to measure how much you press down on the back Try to measure how much you press down on the back legs, how does that affect how high or how far the frog legs, how does that affect how high or how far the frog jumps?jumps?

Make observationsMake observations

Label the next page in your lab notebook Label the next page in your lab notebook Elastic Potential Energy Conversions.Elastic Potential Energy Conversions.

Draw a diagram of your frog and explain, Draw a diagram of your frog and explain, briefly, how you made it.briefly, how you made it.

Make observations about the way the frog Make observations about the way the frog responds in your lab notebook. Think about responds in your lab notebook. Think about what you learned as you “played” with your what you learned as you “played” with your frog.frog.

Practice controlling your frog’s motion until you Practice controlling your frog’s motion until you can predict where it will jump.can predict where it will jump.

Jumping Frog EnergyJumping Frog Energy

1. Where does the energy come from to move your 1. Where does the energy come from to move your frog?frog?

2. Can the amount of energy your frog has be 2. Can the amount of energy your frog has be changed to make it jump at different heights and changed to make it jump at different heights and distances? Explain.distances? Explain.

3. When does your frog have potential energy?3. When does your frog have potential energy?

4. When does your frog have kinetic energy?4. When does your frog have kinetic energy?

5. When does your frog have the most energy? 5. When does your frog have the most energy? Explain your answer.Explain your answer.

6. When does your frog have least energy?6. When does your frog have least energy?

Working FrogsWorking Frogs

Remember, whenever an object has Remember, whenever an object has energy it has the ability to do work.energy it has the ability to do work.

The kinetic energy in your frog as it The kinetic energy in your frog as it moves can be transferred to a small moves can be transferred to a small weight, for example, a washer.weight, for example, a washer.

How much work can a How much work can a jumping frog do?jumping frog do?

Measure the mass of the washer given to you Measure the mass of the washer given to you by the teacher.by the teacher.

Multiply the mass in kg by the gravitational Multiply the mass in kg by the gravitational constant to determine the force of the washer’s constant to determine the force of the washer’s mass. mass.

Record the force in newtons in your lab Record the force in newtons in your lab notebook.notebook.

Push it…Push it…

Suspend your washer on a string where Suspend your washer on a string where your frog can jump up and push it.your frog can jump up and push it.

Design a way to reliably measure the Design a way to reliably measure the distance the push moves the washer.distance the push moves the washer.

DIAGRAM!!!DIAGRAM!!!

Draw a diagram of Draw a diagram of your work your work measuring setup in measuring setup in your lab notebook.your lab notebook.

Go the distanceGo the distance

Record the distance data for each Record the distance data for each successful “working jump”successful “working jump”

Figure out the average distance your frog Figure out the average distance your frog moved the washer and record it in moved the washer and record it in centimeters.centimeters.

Convert that average distance into Convert that average distance into meters (the standard unit must be used meters (the standard unit must be used in the next part of the lab)in the next part of the lab)

Calculations time!Calculations time!

Calculate the amount of work your frog Calculate the amount of work your frog did by multiplying the force of the did by multiplying the force of the washer’s mass by the average distance washer’s mass by the average distance the washer moved.the washer moved.

Work Work (Joules)(Joules) = Force = Force (Newtons)(Newtons) x distance x distance (meters)(meters)

Estimate the energy…Estimate the energy…

Now, you know the energy your frog had Now, you know the energy your frog had stored in it when you compressed the stored in it when you compressed the back legs (minus some for error, air back legs (minus some for error, air resistance and a little loss to sound).resistance and a little loss to sound).

So - who’s frog has the most powerful So - who’s frog has the most powerful kick?kick?