What does it mean to say that mass is conserved during a physical change?

Alright, so mass is a property of a physical body. During physical changes, such as acceleration, force, etc, the mass stays the same since we are not affecting its physical shape, just where it is physics wise. So yeah mass is conserved during a physical change.

Explanation:

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v=ir = 3x15 =45 v

3. dark matter

empty space could also be a simple vacuum