What is a magnetic disc that provides long-term storage for programs and data?

The correct answer is: A HARD DISK

Explanation:

Magnetic Disc stores data of different types and formats that can always be edited or erased at any time. An example of a Magnetic Disc is a Hard Disk.

A hard disk is a type of magnetic storage device inside a computer that store data magnetically usually for the long-term and it could store a large volume of data, though that depends on the size, because it comes in various size. However, it generally allows stored data to be retrieved easily.

this is poiselle's equation from fluid mechanic in physics. mech eng