A-level maths help!

Okay, So I'm am really confused. Does the coefficient of friction change depending on the forces which are applied? As I have seen questions where it does change and you cannot use the same value for mu for the second part BUT I have seen questions where it does change. Can someone clear up when it changes and when it doesn't?

Reply 1

mqb2766

21

Original post by skyeforster15

Okay, So I'm am really confused. Does the coefficient of friction change depending on the forces which are applied? As I have seen questions where it does change and you cannot use the same value for mu for the second part BUT I have seen questions where it does change. Can someone clear up when it changes and when it doesn't?

mu*R is the limiting (absolute) value, so the maximum value the frictional force/resistance can take. It can be less than this, even zero. Maybe think of it like a sponge which can absorb liquid/excess force up to a certain value. The coefficient of friction, mu, depends on the materials and would be unlikely to change in a question.

(edited 10 months ago)

Reply 2

Notnek

21

Original post by skyeforster15

Okay, So I'm am really confused. Does the coefficient of friction change depending on the forces which are applied? As I have seen questions where it does change and you cannot use the same value for mu for the second part BUT I have seen questions where it does change. Can someone clear up when it changes and when it doesn't?

Could it be that in the questions you've seen, the coefficient of friction remains the same but the frictional force varies? In most questions the coefficient of friction remains the same throughout the question.

Let us know if this is the case and you need an explanation for why the friction force could vary.

A-level maths help!

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