A-Level Edexcel Mechanics M1 January 2011 Q6c : ExamSolutions

[haroim]

I think it's because the coefficient of friction (1/2) only acts when the Force is at its maximum which is 120. Now it says that P = 30 so therefore the coefficient has no effect

[ExamSolutions_Maths]

@daniel502669174 Since F max = 1/2 (96) = 48 but F turns out to be 42 N which shows that it had not reached its max value. If it had the particle would have more force acting up the plane than down and would then move up which would be impossible. Hope this makes sense?

[pure_g]

great work sir as always.. I dont even want to imagine how would my revision look like without your help. but I have a qustion, how do we know that the Frictional Force is now F not 1/2R?

[pure_g]

@ExamSolutions thenks for respond, hmm I can see that when its solved but how would you know that you have to find F instead of 1/2R before you start question?