Two ice skaters, Daniel (mass 69.2 kg) and Rebecca (mass 50.8 kg) are practicing

Question

Two ice skaters, Daniel (mass 69.2 kg) and Rebecca (mass 50.8 kg) are practicing. Daniel stops to his shoelace and, while at rest, is struck by Rebecca, who is moving at 13.2 m/s before she collides with him. After the collision, Rebecca has a velocity of magnitude 6.3 m/s at an angle of 53.7 degree from her initial direction. Both skaters move on the friction less, horizontal surface of the rink. What are the magnitude and 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

(A) Applying momentum conservation,

50.8 x 13.2i + 0 = 50.8 x 6.3 (cos53.7i + sin53.7j) + 69.2 vf

vf = 6.95i - 3.73j

magnitude = sqrt(6.95^2 + 3.73^2) = 7.90 m/s

direction = tan^-1(3.73 / 6.95) = 28.2 deg

(B) Ki = 50.8 x 13.2^2 /2 = 4425.7 J

Kf = (50.8 x 6.3^2 / 2 ) + (69.2 x 7.90^2 / 2)

Kf = 3167.5 J

chaneg in ke = kF - kI = - 1258.2 J

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.