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Physics M2 OCR Mechanics

Needhelp

New member
Apr 9, 2012
17
So I have my final maths exam tomorrow and thought I'd do a few new past papers to brush up.

Here is my problem:
Q 5) part ii.............

I worked out the tension in the string which was correct at 2.24N, but when I resolved vertically to find out the normal reaction force on C, I came out with 5.96N. In the solutions they resolved perpendicular to the plane and ended up with 5.26N.
My workings were: T+NCos(20)=0.8g

Any ideas on where I went wrong?

Thanks!!
 

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MarkFL

Administrator
Staff member
Feb 24, 2012
13,775
I have moved this topic, as it is more physics than geometry.

Just to verify, you are actually referring to question 6, correct?
 

Needhelp

New member
Apr 9, 2012
17
Yes!! Sorry Q6) part ii (Blush)
 

Opalg

MHB Oldtimer
Staff member
Feb 7, 2012
2,708
It looks as though you may be neglecting the frictional force at C, which acts in the direction CB (so as to balance the horizontal component of the normal force at C). If you resolve perpendicular to the rod then the frictional force has no component in that direction.