Friction More of Less

It's been a year since I've blogged though we've still been doing Science Saturday events (I've just been too much of a slacker to write about it).  As Noelle's about to finish elementary school for good I'm inspired to do a little back-filling from this last year.  I'll start with her science fair project from this year about friction (in this case I'm just going to post the details in her own words).

Friction More of Less

Question:

What type of material (normal, sand paper, felt, cloth, or rubber) should a kid use if the faster you go on a slide the more fun it is?

Hypothesis:

I predicted that cloth would have the least amount of friction because cloth slides like socks on hardwood floors.

Procedure:

I used a slide, a protractor, a hinge, two long wooden blocks of the same size, four small square wooden blocks, a piece of sand paper, cloth, felt, and rubber. I determined at what angle each material slides at. The higher angles correspond to more friction and lower angles to lower friction.

Results:

The felt block had the lowest amount of fiction because it slid at the lowest angle and the sand paper block slid at the highest angle so it had the most friction.

Follow Up Question #1:

I was surprised that the felt beat the cloth and I wondered if the reason why was that the felt had less surface area touching the slide than the cloth. So I tested two felt blocks with different surface areas to see if it mattered to friction.

Follow Up Results #1:

• Felt #1 (big surface area): 16, 21 degrees
• Felt #2 (small surface area): 22, 26 degrees

I was surprised to find that the bigger the surface area, the smaller the friction.

Follow up Question #2: I also wanted to see the effect on friction when the blocks had more weight. So I doubled the weight by stacking 2 blocks on top of each other and doing the test.

Follow Up Results #2:

No covering: 38, 40 degrees

No covering double weight: 40, 43 degrees

Felt #1: 16, 21 degrees

Felt #1 double weight: 19, 20 degrees

It really surprised me that there was not a huge difference between the normal weight and the doubled weight though they are the same material so they may create the same amount of friction.

Conclusion:

I originally wanted to figure out how to have the most fun on a big slide by finding a way to slide down faster. These experiments told me that of the materials I tested, a felt bag would give me the best ride. I also found that in the bag, you will go faster if you spread your weight out. Finally based on my experiments, I am happy to report that kids should go faster on a slide than

By Noelle Stam

5^th grade Mrs. Cashin

April 18, 2012