Lesson: Chapter 5 — Friction

5.4. Friction in practice 3 of 9 Reset answers

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Question 3

Ball bearings are fitted where a rotating part meets a non-rotating axle rod. How do they reduce friction?

A The balls are made of a material that has no friction B The balls reduce the weight carried by the axle C The balls roll, so the two surfaces do not rub against each other D The balls make the contact area larger

The right answer is the one marked above.

The balls roll, so the two surfaces do not rub against each other. Sliding is replaced by rolling.

No material has zero friction. And a larger contact area would change nothing anyway — activity 03 settled that.

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