Homemade Sciencewith Bruce Yeany

Experiments  /  Come-Back Can  /  Worksheets

Come-Back Can: printable worksheets

Choose the sheet for the learner's age. Each prints on a single page. Build the project first, then fill it in together.

Ages 8-10: Predict, test & record
Name: ______________________Date: ____________

Homemade Science with Bruce Yeany · Come-Back Can · Ages 8-10

Come-Back Can Test Lab

Make a guess, roll your can, and record what it does.

1. Predict: if you roll the can harder, it will come back...

◯ farther◯ about the same◯ not at all

2. Mark a start line with tape. Roll the can with a gentle, a medium and a hard push. Measure how far it goes out and how far it comes back.

PushDistance outDistance back

3. Did the can come all the way back to the start line?

◯ Yes◯ No, it stopped short◯ It rolled past the start

4. Draw what is inside your can: the band, the battery and the two sticks.

5. What did you find out about how hard you push and how far it comes back?

6. Why do you think the can does not come all the way back?

Ages 11-14: Explain & design your own test
Name: ______________________Date: ____________

Homemade Science with Bruce Yeany · Come-Back Can · Ages 11-14

Energy in a Come-Back Can

Use your can and the ideas in "What's going on?" to explain and test it.

1. Describe the energy changes from your push to the can rolling back. Use the words kinetic energy and potential energy.

2. Why must the battery hang down instead of turning with the can?

3. You want to test whether a heavier or lighter weight changes how far the can comes back. Name what you change, what you measure, and two things you keep the same.

4. Design a fair test of one variable (the weight, the push, or the floor surface).

TrialWhat I changedDistance outDistance back

5. Pick one trial: distance back ÷ distance out × 100 = what percent came back? Where did the rest of the energy go?

6. Where else is energy stored by twisting or stretching, then let go to make something move?

Answer guide for grown-ups

Homemade Science with Bruce Yeany · Come-Back Can · Answer guide

Answer guide

Ages 8-10: Come-Back Can Test Lab

  1. Usually farther, because a harder roll twists the band more (a very hard roll can flip the battery over, and then it won't come back well).
  2. Open answer: look for effort and careful observation.
  3. No, it stopped short
  4. Open answer: look for effort and careful observation.
  5. Answers depend on their data; usually a harder push makes it go out farther and come back farther.
  6. Some energy is lost to friction with the floor and inside the rubber band, so there isn't enough to bring it all the way back.

Ages 11-14: Energy in a Come-Back Can

  1. The push gives the can kinetic energy. As it rolls, the band twists and stores it as (elastic) potential energy. When the can stops, the band untwists and turns the stored energy back into kinetic energy in the other direction. Some is lost to friction each time.
  2. The hanging battery holds the middle of the band still while the ends turn with the can, so the band twists and stores energy. If the battery turned with the can, the band wouldn't twist and no energy would be stored.
  3. Change: the weight (e.g. D vs AA battery). Measure: distance back (and out). Keep the same: the same push, the same floor, the same can and rubber bands, the same start line.
  4. Open answer: look for effort and careful observation.
  5. Less than 100%. The rest was lost to friction on the floor and inside the rubber (as a little heat).
  6. Examples: wind-up toys, rubber-band cars and planes, a bow and arrow, a spring, a pull-back toy car.