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

A stubborn, 120 kg mule sits down and refuses to move. To drag the mule to the barn, the exasperated farmer ties a rope around the mule and pulls with his maximum force of 770 N. The coefficients of friction between the mule and the ground are µs = 0.8 and µk = 0.5. Is the farmer able to move the mule?

no

If so, how much force in excess of the required amount did the farmer pull? If not, how much more force does the farmer require?

N

2. Relevant equations

F= Ma

F(fric)= (Coefficient of friction)*N(normal force)

3. The attempt at a solution

I got the answer to the first part of this question through guessing, so I'm not sure if there is actually work invovled there that needs to be used for part 2 that I therefore don't have due to the fact that I guessed. Anyway, I'm not sure how to approach this problem. Using those equations I got answers separately for static friction and kinetic friction, but I don't think either of those is what I'm looking for. My thought is that I can just disregard kinetic for a second because using 770N, only static friction is involved.

Is there a different way to approach this problem??

Thank you so much in advance!

~Phoenix

PS- I do realize that my net force is zero, for in my force diagram all the vectors should equal each other. But, then how is one to get the amount of force needed to actually pull the mule?

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# Homework Help: Stupid Stubborn Mule and his Kinetic/Static Friction

**Physics Forums | Science Articles, Homework Help, Discussion**