Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: When iron filings and sulfur powder are mixed together in any ratio, they form a mixture. No chemical reaction occurs, and both elements retain their individual properties. A magnet can be used to mechanically separate the two elements by attracting the iron filings out of the mixture and leaving the sulfur behind. Answer: magnet
What can be used to mechanically separate the two elements by attracting the iron filings out of the mixture and leaving the sulfur behind?