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### Student Question

What is the difference between weight and mass? Thank you for helping me; I do not understand!!

Physics ## Explanations (1)

• Explanation from Alloprof  Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

There are several differences between weight and mass:

• First, weight and mass do not have not the same unit. To describe the weight, we use the Newton (symbolized by "N"). To describe the mass, we use the gram (symbolized by "g").

• Then, the weight designates a force while the mass designates a quantity of matter. Indeed, the weight is the force of attraction exerted on an object by a celestial body, including Earth .Mass describes a quantity of matter.

• Then, the weight varies while the mass remains the same. Indeed, the weight is calculated with the formula:

$$W = m \bullet g$$

where W represents the weight, m ​​the mass of an object, and g the gravitational acceleration constant of a given celestial body. Thus, while an object will always have the same mass, its weight will depend on the star on which it is located (because it is necessary to take into account the gravitational acceleration constant of this star in its calculation).

Finally, although these two terms are often used interchangeably in everyday language, they are not equivalent.

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