The difference between mass and weight is fairly easy to understand and I’ll probably be able to give you the nuts and bolts of it in just a few short sentences, so let’s get to it.
Mass in a nutshell is the amount of matter that an object like you or me or the table or cat contains. Usually, when we think of mass we often think of weight because on Earth, we can use them interchangeably. But you’ll see in a minute that there is a difference between weight and mass.
Mass often corresponds to size as well, but this is not always the case. For example, if you blow up a party balloon full of air and you blow it up bigger than your head, the mass of that balloon will not be greater than the mass of your head even though the balloon is bigger than your head.
Mass in the scientific sense has a unit of measurement in grams and kilograms though I suppose for us as laymen and women we can use pounds too.
In common everyday speech we often use weight when we are actually talking about our mass. So let’s take a look at what weight really is in the scientific sense.
Weight is not really related to mass in the sense of how much we weigh in kilos or pounds. Weight is actually the force that is applied to an object due to gravity. And the object here could be you and I, a balloon, a bunny or an airplane in the sky.
The unit for measurement is that of force – duh, because as we just discussed, weight is the measurement of the force of gravity on an object. And this unit is known as the newton or N.
Now an interesting thing about weight, it is determined by using the gravity of earth as a standard. This standard is 9.80665 m/s2. And the formula for determining your weight is W=mg, where W is our weight in newtons and m is our mass and g is the gravitational acceleration of Earth’s gravity which as we mentioned is 9.80665 m/s2.
So when you climb on that scale and you’re delighted (or not) with your weight you aren’t really seeing your weight at all but your mass.
So next time someone asks you how much you weigh and you last saw 150 pounds on the scale you should instead tell them that you weigh 666 newtons (roughly) and see if they look at you funny. Though if you’re embarrassed about your weight you could say you weigh 110.5 newtons on the moon. And you could say “newtons on the moon” under your breath so they hardly hear you.
And this brings us to another point. Your mass is a constant because unless you lose or gain a ton of weight or die and get cremated the amount of matter you contain doesn’t change at all whether you are sitting in your pyjamas watching Simpsons’ reruns on Earth or sitting on a lounge chair on the moon.
See, mass doesn’t rely on gravity for it’s measurement, it is solely related to how much matter you contain. Weight on the other hand relies heavily on gravity and because gravity is less on the moon, your weight is less on the moon even though your mass is the same.
And if you ever get to hang out on the Sun because it’s gravity is more than Earth’s your weight will be more than it is on Earth even though your mass stays the same.
Clear as mud?… Excellent 🙂