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I've always found in physics textbooks (and in general too) that when a paragraph or question mentions mass it actually is succeeded by weight of the object in question.

For example,

The mass of the man standing on top of the board is 70kg.

Why is this?

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  • $\begingroup$ Possible duplicate: physics.stackexchange.com/q/43195/2451 $\endgroup$
    – Qmechanic ♦
    Oct 21 '21 at 9:52
  • $\begingroup$ There is no mention of weight in your example. They say mass and give the value of mass. $\endgroup$
    – nasu
    Oct 21 '21 at 10:37
  • $\begingroup$ It is because the two are easy to confuse if you live in a constant gravitational field. People talk about weight all the time when they mean mass. Weight is the easiest way to measure mass. You go on a diet to lose mass. But the scale tells you the weight. You buy groceries by weight for the same reason. When I was in high school, I was astonished when my physics teacher told me that a pound is a unit of force. I had always thought it was a unit of mass. I had never heard of the true mass unit, the slug. $\endgroup$
    – mmesser314
    Oct 21 '21 at 14:56
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Your question is not easy to understand, in textbooks it is understood, that on earth the man has a weight of $m*g$ which matters if he moves upward or downward, his mass matters if he moves horizontally.

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