Why is rolling friction always less than sliding friction?

Question

The last time I asked, people told me that it was due to the difference in surface area. That explanation doesn't make sense to me, because I thought that sliding friction was independent of surface area.

Answer 1

Comparing rolling friction to sliding friction, say, in the case of a car wheel. Rolling friction is composed of the bearings deforming a tiny bit, the tire deforming a tiny bit, and so forth. These parts are designed to minimize friction. Now lock up the wheel, and you have sliding friction, the tire against the pavement. Completely different forces and surfaces! And also THIS friction is designed to maximize friction for starting and stoppping.

You can read lots more about friction here:
http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html

Answer 2

Because sliding friction creates more friction than rolling.

Answer 3

My guess would be that with rolling friction it has built up more momentum and is less likely to be be affected. With sliding friction though it has not built up any momentum.

Answer 4

Hold out your arm like you are going to curl about say.....30 lbs.

You take the weight in your hand....put it in this position and do one curl with it.

Now.....hold out your arm again. I'll stand on a step ladder about 7 feet above you and drop the weight. You catch it in this position and then do a curl with it?

Which one controls the weight easier?
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That's why.