RAM II: Mass vs Weight

Описание: This video shows explains how Atomic Weight is more correctly called a mass than a weight. What is the difference between mass and weight? Although these two words are often confused, they mean very different things. Mass is the amount of matter of an object, whereas weight is its gravitational force of attraction to Earth. The difference can be clearly understood on other planets where gravity is different to Earth’s, such as Mars, where the weights of objects is much less than on Earth. However, an object’s amount of matter remains the same irrespective of the object’s location in the Universe. The video explores different places in the Universe, such as the Moon and deep space, and shows that mass is a more consistent and reliable way to line up the various atoms than weight.

Transcript: In the last video we weighed all the soccer players in a team and lined them up from lightest to heaviest. The Player Numbers show the player’s place in the list, and written at the top. The Player Weights show their weight in kilograms, and written at the bottom.
But we have to clear something up first. The number of kilograms tells us a person’s mass, not their weight. Mass and weight are similar words, but they’re not the same. To get the difference, let’s imagine that Natalie’s becomes an astronaut, …. and that her spacesuit weighs almost nothing. Her mass is 61.9 kg and tells us the amount of matter she’s made of, and this depends on how many and what kind of atoms she’s made of.
On the other hand, her weight is how much gravitational force that Earth pulls down on her with The stretch of a spring would show her weight. Or how heavy she is. Remember, weight is a force, so it should really be measured in the units of force.
But what are they? The units of mass are kilograms, whereas scientists call the units of force Newtons, after the famous scientist Isaac Newton. Many say he is the greatest scientist of all time.
To give you an idea of how big a Newton is, this really heavy suitcase weighs 300N. You can see how much it stretches this spring. How much will Natalie stretch it? Hmmm, it’s about twice as much. She must weigh about 600 N.
If Natalie goes to Mars, Her mass will still be 61.9 kg because she’s still got the same atoms. Her amount of matter hasn’t changed. Natalie didn’t leave any of herself behind. But her weight on Mars is only two hundred and thirty N. She’s a lot lighter.
On the Moon her weight is only one hundred Newtons.
And in deep space, her weight is zero Newtons. She’s weightless!
How come? Well, a gravitational field comes from the planet or moon she’s close to. If Natalie goes a long way from planets and moons, their gravity becomes very weak. Or nothing at all.
What’s Natalie’s mass in deep space?
Her mass is still 61.9 kg because she’s still made of the same atoms. Her amount of matter hasn’t changed.
Here are our 11 soccer players, all weightless in space. Which is better to line them up? Mass or weight? Why?
Not weight, because none of them have any weight. Mass is better to line them up because each player’s mass stays the same everywhere in the universe. It’s more consistent.
OK, all we need to do is change the name from Player Weight to Player Mass, and it’s fixed.
In our last video we pretended that each soccer player was a different kind of atom on the Periodic Table, with their Atomic Number on the top, and Atomic Weight on the bottom. Can you think of a word that we could change here?
We could swap Atomic Weight with Atomic Mass. Both ways of saying it are officially correct, which is confusing.
This video’s job is to tell you that people mix up mass and weight all the time, even scientists. Just remember, whether they say Atomic Mass of Atomic Weight, they’re really talking about the atom’s mass. Because mass stays the same everywhere.
Of course, each player’s mass in kilograms is much bigger than a real atom’s. An atom’s mass is only about a thousand trillion trillionth of a soccer player’s. Natalie’s overall mass of 61.9 kg is equal to the all the tiny masses of her atoms added up. A thousand trillion trillion of them.
In the next video we’ll show how we can measure the incredibly tiny mass of a single atom.