Units of mass and speed

Troubleshooting physics
1

Hello,
I just need to know in which units mass and speed are. I think mass is in kg, but i’m not sure.
Thanks
Turakar

2

kg and m/s

1 Like
3

thanks

4

In the SI system of measurement (the International System of Units), the fundamental unit of mass is the kilogram. A smaller unit, the gram, is also used widely in many measurements. In the English system, the unit of mass is the slug. A slug is equal to 14.6 kilograms.

Scientists and nonscientists alike commonly convert measurements between kilogram and pounds, not kilograms and slugs. Technically, though, a kilogram/pound conversion is not correct since kilogram is a measure of mass and pound a measure of weight. However, such measurements and such conversions almost always involve observations made on Earth’s surface where there is a constant ratio between mass and weight.

Read more: Mass - body, used, Earth, law, system, surface, part

5

Correct me if I’m wrong - but I think that only place where it is actually observable is default value for gravity (-10)? And that is only for unit of length - is there ANY place where unit of weight matters? I think that you can just assume that 1 = 1 ton and everything will work?

6

For example if you’d like to calculate outside of Bullet what forces to apply then it might matter. But mostly it is an interpretation in the application.
http://www.bulletphysics.org/mediawiki-1.5.8/index.php?title=Scaling_The_World

7

It matters also in how it relates to the size of the object. 1 cubic meter at 1 kg is going to behave differently than 1 cubic meter at 1 ton.

…and it matters to more than just gravity in that case because collision restitution will be based off of the relative mass of the objects. I mean, it’s all relative… but I’d be very surprised if behavior was the same for 1 kg versus 1000 kg.