Weight is something that we are all familiar with, it is how “heavy” something is. It is related to, but not equal to your mass. e.g. the astronauts on the International Space Station have the same mass as they did on Earth, but not the same weight.

Confusing? Try to understand it this way: mass is a measure of how much “stuff” you are made of, and weight is that “stuff” multiplied by the force of gravity.

Weight = Mass x Gravitational Acceleration

= Gravitational Pull

However, the weighing scales (typical bathroom scales) are calibrated to divide the weight by the gravity (9.8 m/s^{2}), hence they show you your mass. But if you take them on the moon, they won’t show the same value, because they’ll still be dividing your weight by 9.8 whereas they should divide it by (1/6)^{th} of that value. Hence even though your mass is the same, the value on the weighing scale won’t be.

Another way to define mass is by the concept of Inertia. Inertia, in the literal sense, means to resist or to stay inert.

e.g. if you try to slide a 1 kg block on a road, it does so easily because its mass is less. But if try to slide a block of 100 kgs, it is going to be very difficult because it has more mass. Hence, when a force is pulling on a body, the amount by which that body resists the change in its motion is its mass. The effect of this force is acceleration, the rate of change of that body’s velocity.

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