Using Newton's laws to solve problems

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To solve the problem of pushing a box across the floor at a constant velocity, start by analyzing the forces involved using a free body diagram (FBD). The normal force can be determined by considering the weight of the box and the vertical component of the pushing force, which is affected by the angle theta. The frictional force, which opposes the motion, is calculated using the coefficient of friction and the normal force. As theta increases beyond a certain value, the normal force decreases, leading to insufficient friction to move the box. This critical angle theta can be found by setting the frictional force equal to the horizontal component of the pushing force.
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Homework Statement



"while moving in a homeowner is pushing a box across the floor at a constant velocity. The coefficient of friction is .41. The pushing force is directed in a downward motion at and angle of theta below the horizontal. When theta's value is greater then a certain value, then the box can not be moved, no matter the force. What is this theta.

I don't know how to start this one.
 
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You know that a FBD, and a list of potentially useful eqns is a great way to start. Assuming you have done that, what is the normal force here (the force with which the floor pushes back). From there its easy to get the frictional force. The push must of course be resolved into X and Y components.
 

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