Floating Cannon Ball

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"Why can mercury

make a cannon

ball float?"

 

 

 

 

 

 

 

"Mercury must be

 more dense than

the steel cannonball"

 

 

 

Review

Which force represents the weight force?

 

 

 

Weight - net gravitational force on an object

 

 

 

w = Fg  = 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)
= Fg (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)
= Fg (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 ...

When an object is on the earth,
it is one earth radius away.

 

 

F = Gm1m2
r2

 

Distance from earth to rocket triples so, ....

 

 

 

....weight is 1/9 as great

 

 

 

w = 2000 N

 

(original weight, 18,000 N)

 

 

 

Wringing out Water on the ISS - for Science!

Canadian Space Agency

 

 

 

Bad Science Humor

Omg

 

Ranking Task

Rank the gravitational forces from greatest to smallest.

 

AP Weight

 



Enrichment

www.wpclipart.com

 

Einstein's Conception of Gravity

The Elegant Universe - PBS

 

 

 

Mythbusters Moon Landing Hoax 4 HQ

 


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