Vinny (m= 40 kg) is at rest on ice ( which we'll assume is frictionless) holding a gun ( m=1 kg). Each bullet in the gun has a mass of 20 grams and fires at 400 m/s.
a) How many bullets must he fire to achieve a speed of 6 m/s?
b) How much chemical energy was stored in the unfired bullets assuming 60% of it is transformed into thermal energy?