This is part II of the science lesson on Potential and Kinetic Energy I did with EJ (7) and JD (5). It is based on lesson C-3 in the book Building Foundations of Scientific Understanding by Bernard Nebel. If you missed part one it can be found here.
Let’s go Bowling!
After our lunch break, we talked about a phenomenon the boys had observed at the bowling alley. Bowling is an excellent and fun real world physics lesson!
The boys enjoy waiting for their bowling ball to come out of the ball return. One day there were several unused balls lined up on the return when EJ’s ball appeared and knocked into the first ball setting only the final ball in the line moving; the others remained stationary. They thought that was super cool! At the time my husband discussed what was happening with the balls but I wasn’t sure how much they retained.
We re-created this scenario with some 1″ steel ball bearings I found at a surplus store. I lined up three of the bearings and asked EJ if he could make the last one in line move without touching it. Then I asked him to explain what was happening. He recalled that energy cannot be created or destroyed and therefore the kinetic energy from the first ball had to have been transferred into each subsequent ball in the line. He understood that the other balls couldn’t move because they were blocked by the next ball until finally the last ball was free to use the kinetic energy it received from the first ball.
EJ then devised his own little experiment using the steel balls and a kids chair from Ikea. He created a hyperbolic funnel, sort of. I’m sure everyone has seen those coin funnels that are used for fundraising, usually in science museums. These funnels are essentially a working model of our solar system. How cool is that! This was not part of our lesson plan so I just let him play as we ended part 1 of our lesson.
Plants and Animals
Finally on day two we completed our final objective of the lesson. We needed to relate what we’d learned about energy back to life on our lovely planet Earth. Previously we had discussed the primary difference between the Animal Kingdom and the Plant Kingdom. Namely, that plants make their own food through photosynthesis and animals must eat plants (or other animals) for food. The kids know that plants get the energy they need for photosynthesis from the sun’s light. They also know that light is one form of energy. Now I asked them to put it together and tell me what KIND of energy the light from the sun is. EJ was able to identify that sunlight is kinetic energy, that the sugar was potential energy, and that when we eat the plant we are transferring, or using, its potential for energy into our bodies to do work i.e. kinetic energy. Eureka!
I couldn’t help but extend this part of our lesson even further by asking EJ where he thought the sun got its energy. We discussed that the energy of the sun is chemical energy produce by the reaction of gasses, particularly hydrogen and helium, causing them to burn. Where did the gas get its energy? Where did the energy that caused the big bang come from? These questions are beyond us at this time, but I used the line of questioning to further reinforce the idea that energy is not made, that it is merely transferred from one thing to another.
This questioning also helps to illustrate an important point about scientific discovery. Specifically, that it’s okay that we don’t have all the answers and that THAT is what science is all about! The continued search to discover and explain how our world and universe work.