http://www.xtremepapers.net/CIE/Cambridge O Levels/5054 - Physics/5054_w09_qp_2.pdf can someone plz tell me how to do 7bii?

taking moments about the wall 1*18000 equals to 0.5*F F equalsto 18000 divided by 0.5 check the marking scheme answer should be 36000 N

Force is acting from the center, so to find the center of 3m slab, we will divide 3 by 2 so we get 1.5. We note that 0.5 of the length of the slab is on the right side of the wall. So if we sbtract 0.5 from 1.5 we will get 1 which is the distance from wall from left side where the force is acting. Considering wall as pivot we will apply the formua 1 x 18000 = 0.5 x a. (a is unknown). So we will get a = 36000N. Check this out : http://www.paperspoint.net/o_level/2009 ... 9_ms_2.pdf