In The Feynman Lectures on Physics Vol-1, it is written
How hard it is to get a body going is one thing, and how much it weighs is something else. Weight and inertia are proportional, and on earth's surface are often taken to be numerically equal, which causes a certain confusion to the student. On Mars, weights would be different but the amount of force needed to overcome inertia would be the same
I've been thinking about the last sentence for a while now but just couldn't figure out what it means.
If two bodies have different weights and the gravitational acceleration is same for both since they are on the same planet, then clearly one body is more massive than the other.
Then how is it possible that the amount of force needed to overcome inertia be the same?
Isn't inertia an intrinsic property of a body which is proportional to its mass?