Name                                                                      Balloons and Buoyancy Simulation

Go to  http://phet.colorado.edu/simulations/sims.php?sim=Balloons_and_Buoyancy

and click on Run Now.

Determine what factors make a hot air balloon or a helium balloon float

Student Instructions:

1. Why does a hot air balloon float even though it is so heavy?

2. What makes balloons float when they are full of air but not float when they are deflated?

3. Starting with a hot air balloon, figure out how to make the balloon float. What factors affect the balloon floating or sinking? Explain three of these factors and your understanding of why this works as it does.

4. Move to the rigid hollow sphere. What does it mean that the sphere is “rigid?”

5. Play with the parameters of the simulation and get the sphere to float. How is the sphere floating similar to and different from the floating hot air balloon?

6. How will you get the helium balloon to float? Explain how you plan to set all the parameters to get the balloon floating.

7. Set the parameters as you predicted above. Did it work? If so explain why this worked. If not explain why your predictions didn’t work and what you did to change it.

8. Summarize your findings, how does a hot air balloon that is so heavy float in air?