Kinetic Frictional Force

mardi 29 avril 2014

1. The problem statement, all variables and given/known data



Using the relation ## tan \theta = \mu_k ## what angle should the rope make with the horizontal

in order to minimize the work done per unit distance traveled along the ground.







2. Relevant equations



## W = Fdcos\phi ##









3. The attempt at a solution



I found ## tan\theta = \mu_k ## by finding the derivative of a with respect to ##\theta ## and let it equal 0.



## a = \frac{F}{m}cos\theta - \mu_k (g - \frac{F}{m}sin\theta) = 0 ##



I think ## F = \mu_k F_N ## is a minimum when ## \frac{dF}{dx} = 0 ## and ##\frac{d^2F}{dx^2} > 0 ## . Is this correct? If so how do I use this?





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