A 65kg boy and his 40kg sister, both wearing roller blades face each other at rest. The girl pushes the boy hard, sending him backwards with a velocity of 2.9ms-1 towards the west. Ignore friction.
a. Describe the subsequent motion of the girl.
b. How much chemical energy is converted into mechanical energy in the girl's muscles?
c. Is the momentum of the boy-girl system conserved in the pushing apart process?