Elsa has three metal blocks that look the same. • One of the metal blocks is made of aluminum.
• One of them is made of iron and has been magnetized.
• One of them is made of iron and has not been magnetized.
Elsa does not know which is which.
Describe how she could use a bar magnet to find out which is which.

An experiment was performed on a 2-kg block. forces of 5, 10 and 15 newtons respectively were applied to the block for 5 seconds. describe the difference in acceleration between the three trials. a) the final accelerations will all be the same. b) the final acceleration will triple between the first and third trial. c) the final acceleration will be cut by 1/3 from the first to third trial. d) the final acceleration will increase nine time between the first and third trial.