- #1

dl447342

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- Homework Statement
- You are sliding a block with mass m up a ramp inclined at an angle of theta with respect to the horizontal where the coefficient of static friction between the block and the ramp is mu_s. What is the maximum horizontal force you can apply to the ramp to prevent it from sliding up, assuming theta > 90 - theta_s, where theta_s is the angle between the ramp and horizontal when the force of static friction is maximum.

- Relevant Equations
- Wsin theta - F cos theta + f_s = 0,

-W cos theta - F sin theta + N = 0

I tried using Newton's first law as the net force in both the x and y directions should be zero in this case. In the free body diagram you need to consider weight, friction, normal force, and the horizontal force. I got a result that said that the horizontal force F you apply is at most W(mu_s + tan theta)/(1 - mu_s tan theta), where W is the weight. But this is negative for theta > 90 - theta_s. What does that say about the maximum horizontal force you can apply?