- #1
Patdon10
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Homework Statement
a 20-kg block rests on a 30 degree incline. knowing that the coefficient of static friction is 0.25, determine the magnitude and direction of the smallest force P required to cause the block to start sliding up the incline.
Homework Equations
F = ma
The Attempt at a Solution
I'm trying to solve it using x and y components. For this example, I consider the X direction to be straight up the ramp, and the y to be in the direction of the normal force. The problem is I have 2 equations and ?3? unknowns. How can I solve for Normal force if the normal force is being affected by the pull in the y direction. I've tried to solve this problem many times with no luck. Can someone point me in the right direction?
My teacher told me it would be much easier to solve this using a force Triangle, but I would prefer to use this method. If there were some rule, saying the angle is so-so, because that leads to the least pull this would be a very simple problem.
F_x = Pcos(θ) - mgsin(30) - F_s
F_y = Psin(θ) - mgcos(30) + N
F_s = μN