Question

A metre stick is plvoted about its centre. A piece
of wax of mass 20 g travelling horizontally and
perpendicular to it at 5 m/s strikes and adheres to
one end of the stick so that the stick starts to
rotate in a horizontal circle. Given the moment of
Inertia of the stick and wax about the pivot is 0.02
kg m, the initial angular velocity of the stick is
(1) 1.58 rad/s
(2) 2.24 rad/s
(3) 2.50 rad's (4) 5.00 rad/s​

Answer 1

Answer:

=> Here if we consider wax + stick as a system

=> We can say  that there is no external torque on it so angular momentum is conserved

=> Initial angular momentum of stick + wax = final angular momentum of stick + wax

= Initial angular momentum is given by

∴ Here, m = 20 g

             v = 5 m/s

              r = 50 cm

->  Final angular momentum is given by

=  Here I = 0.02 kg m^2

=  Now, by angular momentum conservation

∴ So the final angular speed of wax + stick is 2.5 rad/s.