Q. Jack and Jill are standing on a crate at rest on the frictionless horizontal surface of a frozen pond. Jack has mass 74.4 kg, Jill has mass 45.1 kg, and the crate has mass 14.9 kg. They remember that they must go and fetch a pail of water, so each jumps horizontally from the top of the crate. Just after each jumps, that person is moving away from the crate with a speed of 4.40 m/s relative to the crate.

(a) What is the final speed of the crate if both Jack and Jill jump at the similar time and in the similar direction? (Hint: Use an inertial coordinate system attached to the ground.) (b) What is the final speed of the crate if Jack jumps first and after that a few seconds later Jill jumps in the similar direction? (c) What is the final speed of the crate if Jill jumps first and after that Jack, again in the similar direction?