TBR 2 question 35

[Joker88]

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Hey guys i was having some trouble understanding the explanation for this question.

35.Which of the following reasons explains why a skidding car takes longer to stop than one that is not skidding?

A. A skidding tire transfers momentum better than a rolling tire
B: The coefficient of static friction between the car's tires and the road surface is greater than the coefficient of kinetic friction
C: The skidding car loses some of the mass of its tires on the road surface
D: The force of kinetic friction is greater than the force of static friction between the car's tires and the road surface

The answer was B. If someone could explain this to me id appreciate it! thanks!

 

[Red Clown]

I think the key is understanding the difference between a rolling tire and a skidding tire. It may seem strange but a skidding tire is being is literally being dragged across the surface, and when something is dragged it is experiences kinetic friction. On the other hand a rolling tire experiences static friction. As each part of the tire just touches the road for a brief moment. During that "touch" the patch of tire isn't moving or skidding in relation to the road, it just touches the road. ( visualizing a rolling tire with static friction is the hard part)

Since static friction has a greater coefficient than kinetic friction. The force the ground has upon a rolling tire is greater than a skidding tire. Since the rolling tire experiences more force it will be able to stop faster than a skidding tire. I hope my explanation made sense.

 

[Joker88]

definitely makes sense. thanks!