Why Does the Ramp Exert Total Force mg Instead of mgcos30 on the Mass?

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The discussion centers on the confusion regarding the total force exerted by a ramp on a mass, specifically questioning why it is mg instead of mgcos30. It is clarified that while mgcos30 represents the normal force, the total force F exerted by the ramp must balance the gravitational force mg acting on the block. Since the block is stationary, the forces must be in equilibrium, leading to the conclusion that the total force is indeed mg. The distinction between normal force and total force is crucial for understanding the problem. This clarification highlights the importance of considering all forces acting on the mass in static equilibrium.
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My exam is in an hour, so quick replies are dearly needed!

http://www.ph.qmul.ac.uk/phy116/Exams/Mid%20Term%20Test%202006%20Answers.pdf
Question 3)a

I would have said the force exerted by the RAMP on the MASS is mgcos30, not mg as my lecturer has said (and it's the same in every paper).

What am I not seeing here? The only thing I can think of is due to the axis of where F is.

Thanks!
 
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The block is not moving, thus a = 0. Also, gravity pulls down on the block with a force equal to mg. If you accept these two facts, balance the forces in the vertical direction and see what you get.
 
I just saw this post, too late for the exam, but I have a comment that may help.

mg cos30 is the normal force exerted by the ramp on the block. But the question is really asking for the total force F exerted by the ramp, which includes the friction and normal forces.

As diazona said, F must balance against the downward, vertical force mg.
 

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