Posted by **Bella** on Wednesday, February 27, 2013 at 1:47pm.

A window washer pushes his scrub brush →−

up a vertical window at constant speed by applying a force F as

shown in Fig. P5.74. The brush weighs 15.0 N and the coefficient

of kinetic friction is μk = 0.150. Calculate (a) the magnitude of →−

the force F and (b) the normal force exerted by the window on the brush.

- physics -
**bobpursley**, Wednesday, February 27, 2013 at 1:49pm
I don't understand your symbology →−

- physics -
**yan**, Wednesday, February 27, 2013 at 1:51pm
where's the picture?

any how, F=uN

brush weighs 15N , 15N=the normal force if the washer doesn't push down. If he/she did push down on the brush with a force F, it would be the cosine of the angle that is pushing down . so yeah draw a free body, and you'll see which forces are required

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**Elena**, Wednesday, February 27, 2013 at 5:36pm
v=const => a=0

N =F(x)•cosα

F(y)•sinα=mg+F(fr)

F(y)=(mg+μN)/sinα

F=sqrt(F(x)²+F(y)²)

- physics -
**Jack**, Thursday, February 28, 2013 at 2:26pm
F is 208.42N normal is 125.14 N

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**Rigel**, Thursday, February 4, 2016 at 11:35am
F*sin(theta) = F*cos(theta) * (mew) + weight

F*sin(theta) = F*cos(theta) * (0.150) + 15

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