What nondestructive testing method requires little or no part preparation, is used to detect surface or near surface defects in most metals, and may also be used to separate metals or alloys and their heat-treat conditions?

Eddy current testing method.

Explanation:

Non destructive testing methods are techniques which makes use of electromagnetic radiation to examine and detect anomalies in a wide variety of articles( metallic or non - metallic) without causing any changes to it. Non destructive testing is used in science and technology fields such as:

- petroleum engineering,

-mechanical engineering,

- forensic engineering,

- aeronautical engineering and

- medicine.

Types of non destructive testing includes

Eddy current testing, magnetic- particle testing, liquid penetrant testing, radiographic testing, ultrasonic testing, and visual testing.

Eddy current testing method is used to detect surface or near surface defects in most metals, and may also be used to separate metals or alloys and their heat-treat conditions.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.