1. The problem statement, all variables and given/known data An astronaut in space weights 100 kg and is holding a cannon which can shoot a 10kg cannonball. The astronaut is moving at 10 m/s. The astronaut wishes to fire the cannonball such that he turns the maximum possible angle. Find this angle in degrees. 2. Relevant equations 3. The attempt at a solution If we consider astronaut and cannon ball to be a system then on that system no external force and torque acts on it so we can use equations for conservation of momentum and angular momentum and energy. I have a confusion, when astronaut fires the cannon an impulsive force(due to recoiling) acts on it, due to which the astronaut rotates. Also as no other torque acts on it afterwards so I think it will go on rotating forever. However I proceeded. I think for turning through maximum angle I think the initial kinetic energy of should get converted to the rotational kinetic energy. For finding rotational energy I need to calculate moment of inertia of astronaut first. But how? Also we can not consider as a point mass. Can we?