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# Forces and Energy: Week 2

For all of the official (and free!) “Science Without A Net” lesson plans please see here.

We are now on to week two of “Forces and Energy”, and I continue to be really impressed by FarrarWilliams’s Science Without A Net plans. Be sure to check them out for yourself! Today we had the added bonus of my husband being home to help with our experiments, and this really pushed the scientific discussion to a much higher level than I would have thought to take it by myself. (Of course, as I often remind my husband, just because you have engineering degree from Stanford doesn’t mean you can find your keys.) But I digress…

Our topic for today was how energy cannot be created, but can be transferred from one form to another. Here are pictures from the experiments we did. I am probably going to splice them together into a larger homemade book about energy in a few days. Our printer is out of ink at the moment, and I’m still waiting for the replacement cartridges to arrive.

## Part 2 of our book on Energy

Energy cannot be created, but it can be transferred from one form to another.

We tried out an experiment in the garage using the tennis ball that hangs from

the string and helps mom park the car in the right place.

Dad pulled the ball all the way to Bruce’s nose. The tennis ball had a lot of potential energy.

Once the tennis ball started swinging, the potential energy turned into kinetic energy.  It never hit Bruce’s nose because the tennis ball could not have more kinetic energy than the potential energy we loaded it up with.

Our next experiment with was with a sock full of rice that we taped to the table. Bruce pulled the sock back and loaded it with potential energy.

Then he let go of the sock and the sock hit the can.

The potential energy turned into kinetic energy, and sent the can rolling.

Next we tried the same experiment, but this time we used the magic can that we made last week.

When the regular can hit the magic can, the magic can rolled back, hit can #1 and then hit the sock. It was a chain reaction! Mom asked why the cans didn’t keep rolling on and on forever, and Bruce knew the answer.

Friction was causing some of the energy to go into the floor. Eventually the cans stopped rolling, and the sock stopped being hit.

The last investigation we did was with solar powered calculators. Bruce’s calculator is very new and works really well. The solar cells are not very big. Mom’s calculator is twenty years old and does not work as well. The solar cells on Mom’s calculator are really big. Maybe that’s because solar technology has improved a lot over the years, or maybe Mom’s calculator needs larger solar cells because it can do fancier things.