A 50 kg child running at 6.0 meter per second jumps onto a stationary 10kg sled. The sled is on a level frictionless surface. 1.FIND VELOCITY AFTER CHILD JUMPS ONTO SLED M1V1+M2V2=(M1+M2)VF 300=60VF VF=5 M/S 2.FIND KINETIC ENERGY of the sled with the child after she jumps onto the sled. KE=1/2MV^2 1/2(60)(5^2)=750J 3.After a short time, the moving sled with the child aboard reaches a rough level surface that exerts a constant frictional force of 54 newtons on the sled. How much work must be done by friction to bring the sled with the child to a stop? WFf=(Ff)(D) =54d find d vf^2=vi^2+2ad 0=50^2 + 2(-54/60)d 1.8d=25 25/1.8 = 13.9M now i got wff=54x13.9 =750J am i correct?