# “Mass is a measure of an object’s ability to resist motion or movement of any kind”

This statement is presented as wrong, but I dont understand why. Specifically, what is the diff between motion and "movement of any kind"? Its to do with a question about inertia. I understand that first law equates objects at rest with moving with constant velocity, but its the wording thats confusing me. What do they mean by "movement of any kind"?

• The trick is to insert the words change in between the words "resist" and "motion." Though that would still not be a fully complete statement, it would certainly come closer for to what you are aiming, I think. – honeste_vivere Feb 8 '16 at 17:31

## 2 Answers

Inertia is the measure of an object's ability to resist CHANGES in motion (acceleration). Mass is directly related to Inertia.

• Inertia is the property and (inertial) mass is the measure? – Farcher Feb 8 '16 at 17:47
• @Farcher that's a good question and I confess I don't know how to answer it. The greater the mass an object has, the harder it is to change its motion. – Mephistopheles Feb 8 '16 at 20:54

I don't know if this will help, but here goes:
Let's say you have a twelve-pound medicine ball, and here on earth you can accelerate that ball to, say, twenty miles per hour. If you then take you and that ball to the moon, the ball will weigh only two pounds. However, you will still only be able to accelerate that ball to the same twenty-mile-per-hour velocity as you did on earth, because while that ball may weigh only two pounds on the moon, it still has twelve pounds of mass, and it's the mass you need to overcome to accelerate it, not its weight. (All this assumes you're in some sort of environment in which you're not encumbered by some sort of space suit.) by

Nit picking trivia: the above is conceptually true. However, let's say you have enough strength to support one hundred pounds. If you're holding that twelve-pound medicine ball on earth, then you have eight-eight pounds of force left over that you can apply to the medicine ball. On the moon, however, you now have ninety-eight pounds of force you can apply to the ball, because you're only using two pounds of force just to hold the ball stationary. (This, of course, assumes you have to use the same group of muscles to support the ball has you do to throw it, and I don't know if this is true.)