1.) A horizontal circular platform rotates counterclockwise about its axis at th

Question

1.) A horizontal circular platform rotates counterclockwise about its axis at the rate of 0.901 rad/s. You, with a mass of 71.9 kg, walk clockwise around the platform along its edge at the speed of 1.01 m/s with respect to the platform. Your 20.5-kg poodle also walks clockwise around the platform, but along a circle at half the platform's radius and at half your linear speed with respect to the platform. Your 17.1-kg mutt, on the other hand, sits still on the platform at a position that is 3/4 of the platform's radius from the center. Model the platform as a uniform disk with mass 90.1 kg and radius 1.97 m. Calculate the total angular momentum of the system.

2.) A uniform rod is set up so that it can rotate about a perpendicular axis at one of its ends. The length and mass of the rod are 0.829 m and 1.13 kg. What constant-magnitude force acting at the other end of the rod perpendicularly both to the rod and to the axis will accelerate the rod from rest to an angular speed of 6.49 rad/s in 9.73 s?

Explanation / Answer

Your angular velocity:
?_y = 0.901rad/s - 1.01m/s / 1.91m = -0.372 rad/s (cw)
poodle's angular velocity:
?_p = 0.955rad/s - (1.01m/s / 2) / (1.91m / 2) = -0.372 rad/s (cw)

your I_y = mr

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