1. The problem statement, all variables and given/known data The horizontal surface on which the objects slide is frictionless. The acceleration of gravity is 9.8 m/s2. Three blocks are sliding on a frictionless horizontal surface: Fℓ----->[Block1-1kg][Block2-7kg][Block3-4kg]<--Fr If Fℓ = 29 N and Fr = 3 N, what is the magnitude of the force exerted on the block with mass 7 kg by the block with mass 4 kg? 2. Relevant equations F = ma 3. The attempt at a solution 29 N - 3 N = 26 N (total force) 1kg + 7 kg + 4 kg = 12 kg (total mass) a= F/m = 26 N/12 kg = 2.166666667 m/s2 (acceleration of all the blocks in the right direction) masses of Block2 + Block 3 = 11 kg F = (11 kg)(2.166666667) = 23.83333333 N (THIS IS THE WRONG ANSWER!) What am I doing wrong?