2.9 Weight

Weight is the force of an objective due to gravity.

For example, Miley Cyrus is 55kg. This is her mass, meaning m=55. Weight is the force due to gravity, which can thus be calculated with the formula F=ma. Acceleration due to gravity (at least on earth) is 9.8m/s² down, meaning a=9.8. Thus, from F=ma, we know F=55*9.8=539N. This means force is 539N down.

Compare this with the acceleration on the moon, defined as a=1.6 rather than 9.8. Using the same formula, we get F=55*1.6=88N. This means force is 88N down.

Note that although the mass is the same anywhere (55kg), the weight (aka force) differs depending on which planet you are on, so long as the acceleration due to gravity differs.