Question

A professional boxer of mass m1 strongly hits a punching bag in the center of m2, it is suspended from a cable. The collision between both bodies is perfectly inelastic. Therefore, this combined system is balanced through a height l.

a) How fast does the boxer hit the bag?

b) If the fist lost all its initial speed when hitting the sack. How high did the sack swing?

c) Find the angular velocity of the bag after the boxer transmitted the full speed of the fist?

You must raise all the equations and clearances to solve the situation.

Answer 1

a) The conservation of momentum yields:

Initially, the bag is at rest, and after the punch both the fist and the bag move with the same speed let's call it V prime, then

b) If all the kinetic energy of the punch was transfered to the bag, by conservation of energy we have:

c) The linear velocity of the bag after the punch would be: