We have been doing a unit on force and motion this month, and the older two boys have been enjoying the experiments!  Our first experiment involved using marbles to study the transfer of energy.  In our second lesson, we learned about friction.  We learned that friction is a force that tries to keep one object from sliding past another.  No surface is perfectly smooth, and so there will always be some amount of friction between two rubbing objects.  We talked about how friction can be useful – we need some friction between our shoes and the ground so that we don’t slip (like walking on ice)!  Then we talked about ways that friction can be harmful, such as the knees wearing out on our jeans when we play on the floor or parts wearing out inside our car’s engine.

Experiment:  How does friction affect how far a car will roll?

Procedure:  We rolled a Playmobil jeep down a ramp and onto a smooth board (the top of a train table).  We measured how far past the edge of the board that the jeep rolled.  Then, we covered the board with a variety of surfaces – a sheet, a towel, and a fleece blanket, and measured how far past the edge of the board that the jeep rolled off each surface.

**Note:  You really don’t need the board.  You can just have a ramp and have a car roll right onto the floor and then place your different “friction” surfaces right on the floor.  Just be sure to measure how far the vehicle travels the same way each time.  We used the board because our bumpy tile was goofing up the jeep!

Aidan had the job of measuring.  We did three trials with each surface, and then I intended to teach Aidan how to find the average of the three trials.  However, we never got to it that day and he just wrote down one (his favorite?) in his chart.  Today we did another experiment and we did learn about averages this time!

Aidan made a chart to record his results.  We found that the towel created the most friction and slowed the car down the most.

Our biggest source of error in this experiment was a cute 3 year old named Owen.  He just couldn’t keep his hands off the set-up!  Afterwards, we let him have it all to himself to roll cars down the ramp, but it wasn’t nearly as enticing then…

Stay tuned!  Experiments on inertia, momentum, and gravity to come!

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  1. Momndani Jan 6, 2015

    Thank you for posting this article on your blog! We just did this experiment on friction today, with huge success! I have a 10 and 7 year old, so we added a couple of things. We used 3 cars (labeled A, B and C). Each car took a single turn on any given friction run...then we did the average. We made theories and conclusions. We discussed our results for quite some time, then notebooked the results. That really made the concept stick! Thank you thank you!

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