Solving a Lever Problem: Need Help from Experts | Join Our Forum!

[Girn]

Please help me guys, I joined this forum just to post this... spent an hour or so trying to get the answers but I can't for the life of me!

Homework Statement

http://imageshack.us/a/img141/9812/20121012003953.th.jpg

Homework Equations

The Attempt at a Solution

http://imageshack.us/a/img211/7388/20121012003920.th.jpg

 

[Simon Bridge]

Summarizing the problem in text avoids making people squint at photographs.

33m beam has two supports
overhangs both by 5m
600kN at extreme right end
900kN at extreme left end
159kN/m over entire length
Calculate support reactions.
...

You seem to have worked the torques...
Where did you get stuck? Work slowly through the math - showing your reasoning.

 

[Girn]

I don't know where I am getting stuck, but I aint getting the answer. I am not sure what I am doing wrong.. I've tried so many different combinations.. obviously the basis for the formula is clockwise movements=counterclockwise movements, but I aint getting the answer.. and 900kN is not at the extreme left end, its 8m from the left end.

 

[Simon Bridge]

Oh I misread that - see the problem with presenting the problem in a photograph?

I'm having trouble treading your working in the photo - I see a 900x8 in there ... that would be the torque about the extreme left end from the 900kN point force. But there is no pivot there: the pivot is 5m, in from that end.

You can reality check your answer by noticing that the total downward force has to equal the total upward force (the beam ain't going anywhere.)

Mind you - taking a look at the answers they give (3297kN and 3453kN) I see they add up to 6750kN upwards... the total downwards force is 6747kN, suggesting that the beam will lift off under a net unbalance 3kN.

I think the distributed force was supposed to be 159.09kN/m ... and somebody rounded off when they shouldn't have.