9: While standing on roller skates, a 60 kg boy pushes his 35 kg little brother...
A 65.0-kg boy and his 40.0-kg sister, both wearing roller blades, face each other at rest. The girl pushes the boy hard, sending him backwards with velocity 2.90 m/s towards the west. Ignore friction. (a) Describe the subsequent motion of the girl. (b) How much potential energy in the girls body is converted into mechanical energy of the boy-girl system? (c) Is the momentum of the boy-girl system conserved in the pushing-apart process? If so, explain how that is possible...