A window washer pushes his scrub brush up a vertical window at constant speed by

Question

A window washer pushes his scrub brush up a vertical window at constant speed by applying a force F?  as shown in the figure (Figure 1) . The brush weighs 14.1N and the coefficient of kinetic friction is 0.120.

1) Calculate the magnitude of the force F? .

2) Calculate the magnitude of the normal force exerted by the window on the brush.

A window washer pushes his scrub brush up a vertical window at constant speed by applying a force F? as shown in the figure (Figure 1) . The brush weighs 14.1N and the coefficient of kinetic friction is 0.120. 1) Calculate the magnitude of the force F? . 2) Calculate the magnitude of the normal force exerted by the window on the brush.

Explanation / Answer

If 53.1 degrees is the angle between horizontal and the handle, then resolve the force applied to the handle into horizontal and vertical components:

Fx=Fcos53.1
Fy=Fsin53.1

Fnormal = Fcos53.1 (since it is not accelerating in the x direction)

Fup - Ffric - wt = (mass)*(acceleration in the y direction)

Fsin53.1 - 0.120(Fcos53.1) - 14.1N = 0

Solving for F

F = 19.3778 N

The normal force is Fcos53.1

Normal Force = 11.634 N

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