Experimenting with Buoyancy
• Buoyancy (boy-an-see) is the upward
force that a liquid exerts on an object.
• If the downward force (weight) of the
object is less than the buoyancy force on
it, the object will float. Things that float are
“positively buoyant.”
• Go to the next slide
Experimenting with Buoyancy
• If the weight of the object is greater than
the buoyant force of the water on it the
object will sink. Things that sink are
“negatively buoyant.”
• If the buoyant force and the weight of the
object are equal the object will hover in
one place. Things like this are “neutrally
buoyant.”
• Go to the next slide
Experimenting with Buoyancy
• Take the box out of your cabinet labeled
“Cartesian Diver”
• Remove the top of the bottle
• Take the bottle to the sink and fill it with
water, Be careful not to make a mess!
• Go To The Next Slide
Experimenting with Buoyancy
• Take the Pipette from the box
• Dip the tip of the Pipette in the top of the
bottle and draw water ¾ of the way up the
long part of the pipette by squeezing the
bulb and letting it go
• Drop the Pipette into the bottle, but make
sure it floats!
• Go To The Next Slide
Experimenting with Buoyancy
• If the Pipette is floating in the bottle, screw the
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cap on the bottle.
If the Pipette sinks, you need to get it out and
remove some water from it.
Once the Pipette is floating in the bottle with the
cap on, take a picture of the assembled
experiment.
Go to the next slide
Experimenting with Buoyancy
• With the top on, squeeze the sides of the
bottle.
• What happens to the pipette inside the
bottle? Record your observations.
• When you squeeze the bottle, what
happens to the water level inside the
pipette? Make sure you record your
observations!
• Go to the next slide
Experimenting with Buoyancy
• Have someone take a picture of your
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experiment in three positions.
Take a picture of the pipette floating at the
top of the bottle.
Take one of the pipette at the bottom.
Try to get the pipette to float in the middle
of the bottle. Take a picture of this as well.
Go on to the next slide
Experimenting with Buoyancy
• Draw a line on the picture of the pipette
where the water is when it is floating
• On the second picture, draw a line where
the water level is when the pipette is at the
bottom of the bottle
• What do you think is happening here?
Write down your observations on the
sheet.
• Go to the next slide
Experimenting with Buoyancy
• When the pressure increases in the bottle
(when you squeeze it) the air in the pipette
is forced to take up less volume. (space)
• When the air pocket gets too small to
support the weight of the pipette, it sinks to
the bottom of the bottle.
• Go to the next slide
Experimenting with Buoyancy
• Submarines sink or rise by controlling the
amount of water in their variable ballast
tanks.
• The diver that you made is just like a minisubmarine.
• Proceed to the next activity