You and your friends are doing physics experiments on a frozen pond that serves
ID: 1539418 • Letter: Y
Question
You and your friends are doing physics experiments on a frozen pond that serves as a frictionless, horizontal surface. Sam, with mass 71.0 kg, is given a push and slides eastward. Abigail, with mass 50.0 kg, is sent sliding northward. They collide, and after the collision Sam is moving at 31.0 degree north of east with a speed of 5.20 m/s and Abigail is moving at 18.0 degree south of east with a speed of 9.80 m/s What was the speed of each person before the collision? Sam's speed: Abigail's speed: By how much did the total kinetic energy of the two people decrease during the collision?Explanation / Answer
consrvation of momentum :
on x axis :
msvsx + mavax = msv'sx + mav'ax
71 * vsx + 0 = 71 * 5.2 cos 31 + 50 * 9.8 cos 18
--> vs = 11.02 m/s ( it's Sam's velocity before collision---> eastward)
on y axis :
msvsy + mavay = msv'syx + mav'ay
0 + 50 * vay = 71 * 5.2 sin 31 - 50 * 9.8 sin 18
--> va = 0.78 m/s ( it's Abigail's velocity before collision ---> northward)
Before collision :
KE = 1/2 * 71 * 11.02^2 + 1/2 * 50* 0.78^2 = 4326.34 J
After collision :
KE' = 1/2 * 71 * 5.2^2 + 1/2 * 50* 9.8^2 = 3360.92 J
--> KE = 4326.34 - 3360.92 = 965.42 J
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