A frictionless puck of mass 1.0 kg travels east at 90 m/s toward an initially motionless puck of mass 2.0 kg. When the pucks are 12 meters apart, the center of mass of the system is located
A) 3.0 m from the motionless puck.
B) 4.0 m from the motionless puck.
C) 6.0 m from the motionless puck.
D) 8.0 m from the motionless puck.
E) 12 m from the motionless puck.

Question

Quizplus · Accepted Answer

The center of mass (COM) of a system can be found using the formula: COM = (m1*x1 + m2*x2) / (m1 + m2), where m1 and m2 are the masses and x1 and x2 are their respective positions from a reference point. Here, if we take the position of the 2.0 kg puck as the reference (x2 = 0), and the distance between them as 12 m (x1 = 12 m), we get COM = [(1.0 kg * 12 m) + (2.0 kg * 0 m)] / (1.0 kg + 2.0 kg) = 12 m / 3 kg = 4.0 m from the motionless puck.

A Frictionless Puck of Mass 1