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## Homework Statement

An air-conditioning unit is fastened to a roof that slopes at an angle of 35° above the horizontal (Fig. 1.33). Its weight is a force on the air conditioner that is directed vertically downward. In order that the unit not crush the roof tiles, the component of the unit’s weight per- pendicular to the roof cannot exceed 425 N. (One newton, or 1 N, is the SI unit of force. It is equal to 0.2248 lb.) (a) What is the maxi- mum allowed weight of the unit? (b) If the fasteners fail, the unit slides 1.50 m along the roof before it comes to a halt against a ledge. How much work does the weight force do on the unit during its slide if the unit has the weight calculated in part (a)

## Homework Equations

Fy=Fsinθ

W=FS

## The Attempt at a Solution

I created x / y axes with x being on the slope of the roof

then try to find F as I know the Fy and the angle so:

Fy=Fsinθ or F=Fy/sinθ

F=425N / sin125 = 425N / 0.82 = 518.3 N

and then for (b)

First find Fx = Fcosθ = 518.3N x cos55 = 518.3N x 0.574 = 297.5N

then

W=FS = 297.5N x 1.50m = 446.25Nm

Does this sound about right??

the results in the answers are: (a)5.2 x 10^2 N

(b) 4.5 x 10^2 Nm

which look similar but i think im missing one zero somewhere?

link to the page of the book:

http://s9.postimg.org/nhklria4f/Screen_Shot_2016_01_13_at_16_02_15.png

Thanks in advance! Hope its ok to post things like this :)