THIS THREAD WAS INCORRECTLY PLACED IN THE CLASSICAL PHYSICS FORUM, SO THERE IS NO TEMPLATE Hi, everyone. my teacher stuck me with these questions and i am need of a little help answering question 2. here's my answers to question 1 first. 1a) a=0, as system would be in equilibrium when F=0 b) F=5mgN, as for a=5m/s the acceleration of B has to equal 2.5m/s and as its in equilibrium F has just got to equal m*a which is 2.5*2mg=5mgN c) F=mga i think my answers are right but if im making a simple mistake let me know. now my attempts at 2. 2a) first, B has to x/2 above the ground for the full system to work so original potential energy is 2mgx/2=mgx assuming A starts on the ground. now its the following kenetic energy bits that are confusing me because there will be two different V's one for A and one for B. VA = 2VB so assuming no energy gets lost to heat via friction whatever all of the gravitational energy plus energy input from F has to turn into kinetic energy so im thinking. mgx + Fx = 1/2mVA 2 + mVB 2 which kind of works if your given enough information. but part B doesn't i don't think. 2b) substituting values into my answer to 2a 98 + 196 = 1/2[ VA 2 + 2VB 2 ] so VA 2 + 2VB 2 = 588N and VA = 2VB so with further manipulation i get VA = 19.8m/s but using logic from question 1. if F=19.6 and B has a mass of 2kg, the acceleration of B = 9.8m/s 2 therefore acceleration of A = 19.6m/s 2 and then using SUVAT. s=10m u=0 v=? a=19.6 m/s 2 v 2 = u 2 +2as v = 23.2m/s which is different. iv tried multiple times and i can't figure out what im doing wrong. im pretty sure its the WEP part not the SUVAT part as im better at that but i do not know. please help.