An ice skater is moving forward at a steady speed of 10 m/s in a straight line. Show and explain your calculation in each of the following.
a) The skater tosses a coin over her shoulder straight (horizontally) behind her. The coin leaves her hand at 5 m/s (relative to the hand). What is the speed of the coin as viewed by a person standing still on the ice?
b) The skater tosses a coin straight up at 5 m/s (as viewed by herself). What is the speed of the coin immediately after it leaves her hand, as viewed by a person standing still on the ice? Show your calculations.