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moments question

i am really stuck on this thing :\ ive drawn a sort of diagram but it doesnt seem to be helping much

a uniform bridge of weight 1200kN and of length 17.0m rests on a support of width 1.0m at either end. A stationary lorry of weight 60kN is the only object on the bridge. Its centre of mass is 3.0m from the centre of the bridge.

Calculate the support force on the bridge at each end

help :s-smilie:

Reply 1

_Ravi_

Take moments from one the supports to find the force on the other support, and then equate what goes up to what goes down to find the original support force that you took moments from (I think that makes sense). The centre of mass of the bridge is 7.5m away from the support that you take moments from.

Reply 2

trance addict

sorry im still not following :\

Reply 3

Dogkicker91

Use one of the edges as a pivot, and treat the question the same as you would normally with a moments question. Then you can resolve vertically to find the force on the other pivot.

Reply 4

prettyboy_bn

how about resolving vertically ?

Reply 5

sel1234

put up your diagram,

I think your equation should look something like this, ; 7.5 x 1200kN + 10.5 X 60KN = 15B

Where B is one of the supports,

1200kN + 60KN = A + B