Question

While moving in, a new homeowner is pushing a box across the floor at a constant velocity. The coefficient of kinetic friction between the box and the floor is 0.368. The pushing force is directed downward at an angle θ below the horizontal. When θ is greater than a certain value, it is not possible to move the box, no matter how large the pushing force is. Find that value of θ.

Answer 1

Answer: 69.8 degree

Explanation:

F*cos(theta)

is your pushing force projected along the x axis and

-F*0.368*sin(theta)

is the friction force generated by the pressure downwards

when F cos(theta) = F*0.368*sin(theta)

the box wont move no matter how large F is, because you are adding no net force along the x-axis

so sin(theta)/cos(theta) = 1/0.368

tan^-1(1/0.368) = theta

theta = 69.8 degrees