1. The problem statement, all variables and given/known data A body of mass 8 kg moves in a straight line on a horizontal frictionless surface. At one point in its path its speed is 4 m/s, and after it has traveled 3 m, its speed is 5 m/s in the same direction. Use work-energy relationships to find the force acting on the mass. 2. Relevant equations PE = mgh KE = 1/2mv2 ME = PE + KE 3. The attempt at a solution Have no idea, do I calculate KE at first then at the second spot and get ΔKE or what? How do i get to finding the force with work-energy relationships???