A man drags a 150-lb crate across a floor by pulling on a rope inclined 15 degrees above the horizontal. a) If the coefficient of static friction is 0.50, what tension in the rope is required to start the crate moving?(adsbygoogle = window.adsbygoogle || []).push({});

The answer is supposedly 68 lb.

I start by assuming the normal force = weight, so Fn = 150 lb. The force of friction operating against the direction of motion is Ff = Fn*coefficient of static friction, which is at its maximum.

So 150*.5 = 75 lb = Ff

Now the x component of the force required to move the crate should be equal to the frictional force (Ff). So Cos 15 = 75/Frope, and Frope turns out to be 77.65 lb. This is wrong, but oddly it is 9.8 off from the correct answer (though I realize this is irrelevant since the problem is in lbs). What am I doing wrong? Thanks

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# Homework Help: Friction problem that's really bugging me

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