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1) Practice Quiz Ch 8 1) Two ice skaters, one with a mass of 45 kg and the other

ID: 778783 • Letter: 1

Question

1)

Practice Quiz Ch 8 1) Two ice skaters, one with a mass of 45 kg and the other with a mass of 60 kg, push off against one another starting from a stationary position. After they have pushed off, the relative speed at which they separate is 0.600 m/s. What is the speed of the 60-kg skater? A) 0.343 m/s 0.257 m/s C) 0.375 m/s D) 0.225 m/s 2) Three masses are located in the x-y plane as follows: a mass of 6 kg is located at (0 m, 0 m), a mass of 4 kg is located at (3 m, 0 m), and a mass of 2 kg is located at (0 m, 3 m). Where is the center of mass of the system? A) (I m, 2 m) b B) (2 m, 1 m) /2 12

Explanation / Answer

Let the velocity of 45 kg and 60 kg skater be v and V respectively.

As they start from rest , their initial momentum = 0
Finallly momentum = 45 v +60 V = 0
   v = -4 V / 3

Also relative velocity of separation = 0.600 m/s
Relative velocity = V- v = 0.600

Substitute the value of v from equation.

7V/3 = 0.600
V = 1.80 / 7

= 0.257 m/s

Option (B) is correct.