Suppose you have one magnet in a straw with its South pole pointed upward. What would happen if you put another magnet into the straw with it's North pole pointed downward?
a. The magnets would be attracted to each other.
b. The magnets would become demagnetized,
c. The second magnet would be pushed out of the straw.
d. The magnets would repel each other.

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?