Help me with tomorrows physics exam!

[Adi]

Aye, I'm pretty rusty on the structures and materials section, can never work out them stupid ladder problems. Can anyone give me some tips, :lol:.

Firstly, I work out the horizontal and vertical components right, and then I just use them to work out the final forces?

Confused

Adin

 

[wombat]

Firstly, I work out the horizontal and vertical components right, and then I just use them to work out the final forces?

More or less. Just remember that for equilibium,
sigma Fx = 0
sigma Fy = 0
sigma Fz = 0 (obviously doesn't apply if working in 2 dimensions)
sigma Ma = 0

Oh, and where's Steve? Turns out he's not entirely useless after all

 

[tu plang]

hmmm ladder aye.... explain more.

if you mean the one where u have a ladder leant against a wall and you are given its mass and the coefficient of friction between it and the ground and you are to find how far up a person of given mass can climb?

if so i can take u through that... else.... i dono

 

[Scully]

I think i might have a vague idea of what you are going on about but not fully. maybe if you showed us a sample question I could help you

 

[®ider]

my teacher says you wont get a question like this on the finaly year exam but anway heres the stuff.
Hard to explain via internet.
The formula is in your text book for ladders ; Fwall=W/2tan0(otheter)

 

[Adi]

Yeah, pretty much what tu plang is saying.

Except that they won't give us a frictional force. I just have trouble knowing what vertical/horizontal components i need to work out.

Say there is a 3m ladder inclined at 70* to the horizontal against a wall with a person weighing 700 newtons 2 metres up the ladder. Work out the wall reaction force, ground reaction forces, and so on...

Adin

 

[tu plang]

aaaah k, im not too sure about that myself as we havent dont anything like that but have done lots on the same concepts.

add me to msn tuplang@gmail.com and we can have a chat.

 

[S.]

hmmm ladder aye.... explain more.

if you mean the one where u have a ladder leant against a wall and you are given its mass and the coefficient of friction between it and the ground and you are to find how far up a person of given mass can climb?

if so i can take u through that... else.... i dono

Does that even happen? I cbf doing the calculations of moments and whatnot, but seems to me that sigma F(y) would be constant, thus constant frictional force at the ground (assuming we're neglecting frictional force on the wall...?) - what am I missing? Can you post up an actual question for us?