The velocity of the Sheila's 5.667 m/s.
Since there is no net force on the system, so we can consider it as perfect elastic collision.
let the mass of the bike is m, according to question after the collision the bike is completely stopped, therefore final velocity of the bike is 0
According to the law of momentum conservation, momentum of sheila and her bike before and after collision must be conserved.
Momentum before collision= momentum after collision
340=m*0+60*v
v=5.667 m/s
