Solve Q5 Part II Maths Exam: Normal Reaction Force on C

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Discussion Overview

The discussion revolves around a problem from a maths exam concerning the calculation of the normal reaction force on point C in a physics context. Participants are exploring the resolution of forces, particularly in relation to tension and friction, within the framework of the problem.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant calculated the tension in the string as 2.24N and the normal reaction force on C as 5.96N, but noted a discrepancy with the provided solution of 5.26N.
  • The participant's equation for vertical resolution was T + N * Cos(20) = 0.8g, raising questions about the accuracy of their approach.
  • Another participant suggested that the first participant may be neglecting the frictional force at C, which could affect the resolution of forces perpendicular to the rod.
  • Clarification was sought regarding the specific question number being discussed, confirming it was Q6 part ii.

Areas of Agreement / Disagreement

There is no consensus on the correct calculation of the normal reaction force, as participants have differing views on the factors that should be considered, particularly regarding friction.

Contextual Notes

The discussion highlights potential missing assumptions regarding the role of friction and the method of resolving forces, which may affect the calculations presented.

Needhelp2
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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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I have moved this topic, as it is more physics than geometry.

Just to verify, you are actually referring to question 6, correct?
 
Yes! Sorry Q6) part ii (Blush)
 
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.
 

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