hi, i've approach the first question, but i don't know how to start w/ this question. I already have my body diagram and everything. Could someone tell me how ?(adsbygoogle = window.adsbygoogle || []).push({});

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Consider a lawnmower of weight which can slide across a horizontal surface with a coefficient of friction . In this problem the lawnmower is pushed using a massless handle, which makes an angle with the horizontal. Assume that , the force exerted by the handle, is parallel to the handle.

Take the positive x direction to be to the right and the postive y direction to be upward.

http://session.masteringphysics.com/probhtml/MFS.cf.8_a.jpg [Broken]

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The first question...

Find the magnitudeFh, of the force required to slide the lawnmower over the ground at constant speed by pushing the handle. Express the required force in terms of given quantities.

>>> For this I got

[tex]Fh=(-(\mu*w))/(-cos(\theta)+\mu*sin(\theta))[/tex]

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This question I've problem with

The solution forFhhas a singularity (that is, becomes infinitely large) at a certain angletheta critical. For any angle [tex]\theta>\theta critical [/tex] , the expression forFhwill be negative. However, a negative applied forceFhwould reverse the direction of friction acting on the lawnmower, and thus this is not a physically acceptable solution. In fact, the increased normal force at these large angles makes the force of friction too large to move the lawnmower at all.

Find an expression for [tex]tan(\theta) critical[/tex]

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# Homework Help: Help w/ this force problem please

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