# Virtual Car Homework #3

 This is an individual assignment. You are encouraged to discuss the question as a team, but be sure to write the answers in your own words.

# Traction

We have discussed the issue of traction a lot, and we discussed how traction is determined by the weight on the drive wheel multiplied by the coefficient of static friction between the tread and the floor. In other words,

Traction (lb) = Weight on wheel (lb) * coefficient of static friction.

This is a pretty simple equation. Doesn't it seem like some other things would affect traction too? For example, how about the width of the wheel? Or the amount of area of the tire tread that is actually contacting the floor? Neither of these things is in our equation.

1. The car your group built on the first day probably had rubber bands around the edge of each wheel to give more traction. Some groups had only one rubber band around each wheel, but there was room to add two or three more of them, side by side. What would this do for the car's traction? Explain your reasoning.

2. Professional race cars, like the ones that compete in the Daytona 500, have very wide wheels, and it leads to better traction. But, physics says that traction = (friction coefficient) * (weight on wheel). In other words, width is not in the equation, but somehow, the extra width gives the race drivers more traction. Where do you think the race car's increased traction comes from?

3. Virtual Car uses the equation below to compute traction:

Traction (lb) = Weight on wheel (lb) * coefficient of static friction.

Yet, if you change the diameter of the drive wheel, the computed traction changes slightly (try it). Why, if diameter is not in the equation?