Which force represents
the weight force?

Weight - net gravitational force on an object

w	=	F_g	=	mg
		(N)		(kg)(m/s²)

g = acceleration due to gravity

Earth: g = 9.8 m/s²

Moon: g = 1.6 m/s²

Apollo 11 astronaut Edwin Aldrin stands near the leg of the lunar module on the Moon. Despite the fact that the backpacks and astronauts only weighed 1/6 on their 350 pound Earth weight, their center of gravity was shifted so they had to lean slightly forward to balance. Footprints are clearly visible in the foreground.

(Apollo 11, AS1140-5902)

slope = g

g (m/s²)	=	F_g	(N)
		m	(kg)

Mass - amount of matter an object possesses

Weightless
Not Massless!

Did you know that an astronaut can be up to 2 inches taller after returning from space? Why?

The cartilage disks in their spine
expand in the absence of gravity

Sciencesational

What is the relationship
between mass and distance?

Choice 1
Mass is not affected by distance
(only weight)

1 kg ≈ 2.2 lbs

University of Michigan

1 lbs ≈ 5 N

Average Senior Weighs

120 lbs ≈ 600 N

Finding acceleration
due to gravity using weight

Ex) A satellite having a mass of 25. kg experiences a gravitational force of 200 N.

Find the acceleration due to gravity at this location.

Ex) A satellite having a mass of 25. kg experiences a gravitational force of 200 N. Find the acceleration due to gravity at this location.

g (m/s²)	=	F_g	(N)
		m	(kg)

g = 200 N/25 kg

a = 8 m/s²

or 8 N/kg

Ex) A rocket weighs 18,000 N at the earth's surface. If the rocket rises to a height where its distance from the earth is 3 earth radii, its weight will be ...