Which is the right answer of R?
Im bit confused. In M1, I was told to use the Second method, which is right for M1.
But Im doing M2 atm, and the solution uses the first method.
Can someone explain?
Thanks for your help.
Remember, if the block is sliding down the ramp, the force is pointing down (parallel) to the ramp. In this case, the force components perpendicular to the ramp should sum to zero. If you draw the free body diagram, you get R = 85gcos(27).
If it is the angle of a ramp in a turn, then the force is horizontal (pointed directly towards the center of the circle). In this case, the vertical force components should sum to zero. If you draw the free body diagram, you get R = 85g/cos(27).
Also, usually R means radius and not normal force. I would suggest changing the notation to avoid confusion.