A horizontally flying bullet of mass m gets stuck in a body of mass M suspended by two identical threads of length l (figure).
As a result, the threads swerve through an angle `theta`. Assuming `mlt ltM`, find:
(a) the velocity of the bullet before striking the body,
(b) the fraction of the bullet's initial kinetic energy that turned into heat.

Explanation

From conservation of momentum, for the system (bullet+body) along the initial direction of bullet
`mv_0=(m+M)v`, or, `v=(mv_0)/(m+M)`