Lighter-Than-Air Flying Devices
Background
• Vehicles designed to travel through air are
termed aircraft.
• There are two types of aircraft:
• 1. those that fly through the air
• 2. those that float in air.
• Hot air balloons and helium airships float in air.
• The density of these aircraft is less than the
density of the air itself.
• These aircraft which stay afloat by the buoyant
force of air, are called lighter-than-air aircraft.
• Buoyancy is based on the idea that less dense
objects will float in a more dense fluid.
• A Styrofoam block, for example will float in
water because the Styrofoam is less dense
than water.
• In the same way, a helium balloon will float in
air because helium is less dense than air.
• Hot air balloons use propane tanks to heat the
air in the envelope, or fabric part, of the
balloon.
• As this air is heated, it expands and becomes
less dense than the surrounding air, allowing
the balloon to rise off the ground and floats in
the air.
• Gas balloons are filled with a low-density gas.
• Hydrogen was used in the past in ships such as
the Hindenburg.
• However, hydrogen easily ignites and was
found to be the cause of the tragic explosion
of the Hindenburg.
• Today helium is used in ships such as the
Goodyear blimp.
Activity One
•
•
•
•
What is this object called?
How does a hot air balloon move?
Does it fly through air or float in the air?
What do you think helps the balloon to float in
the air?
• What is the envelope, or fabric part, of the
balloon filled with?
• What do you know about hot air?
• Propane tanks are used to heat the air in the
balloon.
• When this air is heated, it expands and
becomes less dense, or “lighter,” than the air
around the balloon.
• This allows the balloon to float.
• Warm air expands and becomes less dense.
• Hang two paper bags upside down and have a
light source placed beneath one bag.
• Observe what happens.
• What do you think will happen when the light
is turned on?
• Where will the heat come from?
• Where will the heat go?
• What do you think will happen to the bag?
• Test your predictions.
• Describe on 2.3.3.
• The air in the bag with the lamp under it will
warm from the heat of the light bulb.
• As it warms, the air expands, becoming less
dense than the air surrounding it and the air
in the other bag.
• As a result, this end of the balance scale will
rise as the bag begins to float.
Activity two
•
•
•
•
What is this object called?
How does it move?
Does it fly through air or float in air?
What do you think helps the blimp to float in
air?
• What is the blimp filled with?
• What do you know about helium?
Helium
• Helium Balloon-Helium is less dense that air
therefore it floats.
• Lighter than air aircraft have special controls
to manage their motion through air.
• They are able to float at different altitudes
depending on how the pilot controls the
density of the aircraft.
• What would happen if I let go of the helium
balloon?
• How high do you think it would travel?
• Will it move to the ceiling of the classroom?
• Of we were outside, would it travel farther up
in the sky?
• How could you control the balloon so that it
did not float all the way to the ceiling?
• Challenge- Experiment with the balloon to see
if you can control it?
• Activity sheet -2.3.4.