Posted by Eric on .
two skaters, each of mass 55 kg, approach each other along parallel paths separated by 3.8 m. They have opposite velocities of 1.9 m/s each. One skater carries one end of a long pole with negligible mass, and the second skater grabs the other end of it as she passes. The skaters then rotate around the center of the pole. Assume that the friction between skates and ice is negligible.
(a) What is the radius of the circle they now skate in?
(b) What is the angular speed of the skaters?
(c) What is the kinetic energy of the two-skater system?
(d) Next, the skaters pull along the pole until they are separated by 0.7 m. What is their angular speed then?
(e) Calculate the kinetic energy of the system now.
(a) 1.9 m
(b) w = V/R = 1.0 rad/s
(c) 55*(1.9)^2 Joules
(d) angular momentum is conserved and they speed up by a factor 3.8/0.7
(e) Do the numbers. Kinetic energy increases by a factor equal to the square of the velocity incorease factor.