Timmy the angry teen twirls a dead rat (mass = 2 kg) attached to a rusty chain (length=1m) in a vertical circle. With what velocity should Timmy rotate the rodent so that the chain just goes slack (no force in the chain) at the top?

If a small-diameter open glass tube is partially immersed in a vessel containing mercury, the surface of the mercury inside the tube will be a. lower than the mercury in the vessel, and shaped like the inside of a bowl. b. higher than the mercury in the vessel, and shaped like the inside of a bowl. c. lower than the mercury in the vessel, and shaped like the outside of an umbrella. d. higher than the mercury in the vessel, and shaped like the outside of an umbrella.