A 65 kg box that is resting on a level floor must be moved. The coefficient of s

Question

A 65 kg box that is resting on a level floor must be moved. The coefficient of static friction between the box and the floor is 0.40. One way to move the box is to push down on it at an angle 9 with the horizontal. Another method is to pull up on the box at an angle 9 with the horizontal. Explain why one method is better than the other. Calculate the minimum force necessary to move the box by each method if theta = 30 degree and compare the answers with the result when 9 = 0 degree. N (pulling up at 30 degree ) N (pushing down at 30 degree ) N (pulling at 0 degree )

Explanation / Answer

a) pulling up is better since that will reduce the normal force which will in turn reduce the frictional force3 b) if pulling up forces in the y direction N + F sin(30) - mg = 0 forces in x: Fcos(30) = friction (in order to start) F cos(30) = u N = u (mg - F sin(30)) Fcos(30)=0.4*(65*9.81-F*sin(30)) solve for F F=239.26 N if pushing down sign in y equation flips Fcos(30)=0.4*(65*9.81+F*sin(30)) F= 382.96 N if at 0 degrees F = friction = u mg F = 0.4*65*9.81=255.06 N

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