Two ice skaters. Daniel (mass 60.0 kg) and Rebecca (mass 45.0 kg) are practicing

Question

Two ice skaters. Daniel (mass 60.0 kg) and Rebecca (mass 45.0 kg) are practicing Daniel stops to tie his shoelace and, while at rest, is struck by Rebecca, who is moving at 14.0 m/s before she collides with him. After the collision, Rebecca has a velocity of magnitude 8.00 m/s at an angle of 55.1 from her initial direction. Both skaters move on the frictionless. horizontal surface of the rink. What is the magnitude of Darners velocity after the collision? What is the direction of Daniel's velocity after the collision? What is the change in total kinetic energy of the two skaters as a result of the collision?

Explanation / Answer

conserving momentum in horizontal direction

initial momentum = final momentum

45x14 = 45x8 x cos55.1 + 60 x Vx

Vx = 7.067 m/sec

conserving momentum in vertical direction

0 = 45x8xsin55.1 + 60 Vy

Vy = 4.92 m/s

a)

speed of daniel

V = sqrt (Vx^2 + Vy^2)

V = 8.611 m/s

b)

theta = arc tan Vy/Vx

theta = 34.8 degree

c)

Final KE - Initil kinetic energy

delta KE = 0.5 (60x7.067x7.067 + 45 x8x8) - 0.5 (45x14x14)

delta ke = -1471.72 J

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