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Name: Aneta
Status: educator
Grade: 6-8
Country: Australia
Date: Summer, 2011

Do wider tyres decrease breaking distance because of their larges (surface area) and contact with the road? What simple classroom experiment can I conduct to show this to my upper primary school students? I was considering pulling 2 objects with the same weight but different surface area across the same surface and measuring the force required with a spring scale

Wider tires do not directly relate to frictional forces. There ARE other mechanics involved.

If you agree that frictional forces are proportional to the Normal force...and that the Normal force is just the weight (support force) of the tires (in the simplest case)...then for dragsters which would have the mechanics (spoilers or stabilizers) to maintain a constant force over the surface area...then it follows that a constant pressure would yield a greater force given the larger surface area.

Pressure = Force / Area => Force increases as Area increases if Pressure is constant. This only works if the dragsters have stabilizers to maintain a constant Force of the tire over a given area. Kinda tricky...but way cool. =)

Alex Viray

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