1.

One ice skater of mass m moves with speed 2v to the right, while another of the same mass m moves with speed v toward the left, as shown in figure I. Their paths are separated by a distance b. At t = 0, when they are both at x = 0, they grasp a pole of length b and negligible mass. For t gt 0, consider the system as a rigid body of two masses m separated by distance b. as shown in figure II. Which of the following is the correct formula for the motion after t = 0 of the skater initially at y = b//2 ? (I)

Answer»

`x = 2vt, y = b//2`
`x = vt + 0.5 b sin(3vt//b), y = 0.5b cos(3 vt//b)`
`x = 0.5 vt + 0.5 b sin(3vt//b), y = 0.5 b cos (3vt//b)`
`x = 0.5 vt + 0.5 b sin(6vt//b), y = 0.5 b cos(6vt//b)`

Solution :Frome conservation of linear momentum
`2 m v_(cm) - m (2v) - mv`
`v_(cm) = (v)/(2)` towards RIGHT
from conservation of angular momentum
`J_(F) = J_(i)`
`I omega = 2 mv (b)/(2) + mv (b)/(2)`
`2 m((b)/(2))^(2) omega = (3)/(2) mvb rArr omega = (3v)/(b)`.
it will have TRANSLATION and rotational motion about `C.M`
`x = v_(cm) t + (b)/(2) sin omega t rArr x = 0.5 t + 0.5 si n(3vt)/(b)`
`y =(b)/(2) cos omega t rArr y = 0.5 b co s (3vt)/(b)`.

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