Two ice skaters, Daniel (mass 65.0 kg) and Rebecca (mass 45.0kg), are practicing

Question

Two ice skaters, Daniel (mass 65.0 kg) and Rebecca (mass 45.0kg), are practicing. Daniel stops to tie his shoelace and,while at rest, is struck by Rebecca, who is moving at 13.0 m/sbefore she collides with him. After the collision, Rebeccahas a veocity of magnitude 8.00 m/s at an angle of 53.1 degreesfrom her initial direction. Both skaters move on africtionless, horizontal surface of the rink. A. What are the magnitude and direction of Daniel's velocityafter the collision? B. What is the change in total kinetic energy of the twoskaters as a result of th collison? Two ice skaters, Daniel (mass 65.0 kg) and Rebecca (mass 45.0kg), are practicing. Daniel stops to tie his shoelace and,while at rest, is struck by Rebecca, who is moving at 13.0 m/sbefore she collides with him. After the collision, Rebeccahas a veocity of magnitude 8.00 m/s at an angle of 53.1 degreesfrom her initial direction. Both skaters move on africtionless, horizontal surface of the rink. A. What are the magnitude and direction of Daniel's velocityafter the collision? B. What is the change in total kinetic energy of the twoskaters as a result of th collison?

Explanation / Answer

45*13 = 45*8*cos53.1 + 65*v*cosx

momentum conservation in veritcal direction:

45*8*sin53.1 = 65*v*sinx

v sinx = 4.42

v = 4.42/sinx

45*13 = 45*8*cos53.1 + 65*v*cosx

45*13 = 45*8*cos53.1 + 65*(4.42/sinx)*cosx

x = 37.91 degree

v = 7.19 m/sec

change in KE:

Change in KE = (.5*45*13^2) - (.5*45*8^2 + .5*65*7.19)^2 = 682.37J

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