Weight vs. Mass

Mass and weight are very different.

Mass = the matter in an object. Mass is measured in kilograms.

Weight results from gravity pulling on a mass. Gravity gives masses weight. Weight is a force! Weight is measured in Newtons.

Weight is calculated by multiplying the mass of an object by the acceleration due to gravity. Weight = mg.

On Earth, the acceleration due to gravity is 9.8 m/s/s.  On the moon, the acceleration due to gravity is 1.622 m/s/s. Earth’s larger mass results in a larger acceleration due to gravity as compared to the moon. In other words, you weigh more on Earth; you would weigh less on the moon. For instance, if you take a 10 kg bowling ball to the moon, it would still have a mass of 10 kg. However, its weight would be much less because the moon’s gravity is relatively weak.

 On Earth Mass on Earth = 10 kg Acceleration due to gravity = 9.8 m/s/s Weight on Earth = mg Weight on Earth = 10 * 9.8 Weight on Earth = 98 Newtons On the Moon Mass on Moon = 10 kg Acceleration due to gravity = 1.622 m/s/s Weight on Moon = mg Weight on Moon = 10 * 1.622 Weight on Moon = 16.22 Newtons 100 kg Mass = the amount of material in an object. Mass is typically measured in kilograms 100 kg Weight = mass x gravity = 100 kg x 9.8 m/s/s = 980 Newtons

## * Falling appears to be different for different objects. For instance, which falls faster, a pen or a piece of paper? Why might one fall faster than the other?
* In real life, when do you experience something like free-fall? For how long?
* Which falls faster, a one-ton plane or a ten-ton plane?

------------------------------------------------------------------------

# VOCABULARY

acceleration change in speed during a certain period of time
ascent going up
descent going down
force that which, when acting alone on an object, causes a change in the motion of the object
gravity force on Earth which pulls all objects toward its center
orbit falling around and around Earth
resistance a force opposing the motion of an object or opposing the forces trying to set an object in motion
weightlessness feeling or being observed as having no weight