Forces on a window held by 3 suction cups

[Drizzy]

Homework Statement

Draw the forces on a window

The scenario is that I have 3 suction cups on the window to tale it down. And i don't know where the "normalforce" is. I forgot to draw the force of the suction cups

Homework Equations

The Attempt at a Solution

 

[BvU]

Hi,

The suction cups must be located somewhere. Also, I find it hard to believe the Fn and Ff working lines in your sketch. Please elaborate ...

 

[Drizzy]

Does Fn hav to be opposite of Fg?

 

[BvU]

Opposite meaning working on the left pane if the other is working on the right pane ? Or do they grab along the same line ? Or are there more than one friction forces aat work ?

From the picture I can't see if the window is in static equilibrium or if it's crashing down with thunderous speed (probably the former )

 

[Drizzy]

It is not supposed to move. If I look out of my bedroom window there is a downward force (Fg) and a upward force which is the friction. The window has suction cups om the outside to try to remove the window. So there is also a force outside cus someones is pulling. So i am wondering where Fn is. It must be opposite of the pulling force right?

 

[BvU]

Sorry to have still more questions, but I can't form a complete picture yet:

which way is the someone outside pulling ? Can you post a more complete picture ? Is it sensible to also draw a side view, or are all forces verical ?

 

[Drizzy]

http://imgur.com/a/p9SU3
http://imgur.com/a/p9SU3

Here are the pictures. Fg is down and the friction force is up. Outside there are three things stuck on thw window so they can pull it out. So i am wondering where Fn is

 

[BvU]

Found a window picture:

If you pull on the suction cups in an outward direction, that is a horizontal force. The jambs provide the normal force . So a side view is indicated !

Friction force is up, you say. How do you know ? And is it offsetting Fg completely ?