1. Conestoga Valley High School Aviation Technology Physics Behind Hot Air Balloons

2. Today’s Topics Displacement Buoyancy Density Parts of a Hot Air Balloon

3. Air and Fluid? Have very similar characteristics Flow easily Conforms to the shape of its container Yields readily to pressure Has particles that move easily and change position without dividing mass Fluid Displacement Object placed in a fluid will push some of the fluid to the side (displaces) Fluid pushes back (upthrust) If the weight of displaced fluid and upthrust is the same weight the object will float

4. Archimedes Principle Greek mathematician (287-212 B.C.) “The buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object.” Balloons rise because the balloon displaces a fluid(air) that is heavier than what the balloon and payload weigh Example: Paper ball vs. Sheet of Paper

5. Density Density of Hot Air Density is a measure of the amount of matter in an object (its mass) compared to it volume (size). As air is heated it becomes less dense then cooler air Less Dense=fewer molecules that are crowded in the same space The cooler the air is outside the more efficient the balloon will be.

6. Parts of a Hot Air Balloon Three Basic Parts Envelope The balloon fabric which holds the hot air in. Parts of a Hot Air BalloonBalloon AssemblyHeating the Balloon Burner The piece of equipment which propels hot air into the envelope. Basket Where the passengers and pilot stand. Balloon Launch

7. Lifting Power Lift of Hot Air per 1,000 cubic ft. Heated air to 175 deg. F can lift 16.2 lbs. Example:65,000 cubic ft balloon can lift 1,000 lbs 65000/1000=65 65x16.2=1,053 ~ ~ How large would a balloon have to be to lift you? How much could a 30,000 cubic ft balloon lift Hint: Use Cross Multiplication 486 lbs

8. Lifting Power How much weight can your hot air balloon lift? Use the following formula to find volume 4/3x3.14(r^3) Your balloons radius is 1.25’ ~ ~ 8.2 cubic ft. Use cross multiplication to find lift capacity.13 lbs 1/8 of a lb.

9. Review How is air similar to fluid? As air is heated it becomes less dense? T/F Even though two objects may have the same volume they may have completely different masses? T/F What are the three major parts of a hot air balloon? Flow easily Conforms to the shape of its container Yields readily to pressure Has particles that move easily and change position without dividing mass Envelope, burner, basket