Did you ever want to be a rocket scientist? Thanks to the Internet you can be a rocket scientist—just point and click. You also need to know something about gas pressure. Pressure is force per unit area. The greater the pressure the greater the force per unit area of surface. The SI unit for pressure is the pascal (Pa). The atmosphere at sea level exerts a pressure of 101 kPa. Among non-scientists in the United States, a more common unit of pressure is pounds per square inch, or psi. Atmospheric pressure is 14.7 psi.

All rockets are powered by pressurized gas of some kind. When the gas is released in one direction, the rocket moves in the opposite direction. In this Internet activity you will test-fire a virtual bottle rocket that contains only water and pressurized air. You will explore how pressure affects the rocket's height.

1. How does pressure affect the height a rocket can reach?
   
   Go to Rockets Away! and select the link for Launch Web Demo Rocket. Place 32 ounces of water in the rocket and pressurize it to 25 psi. How high did the rocket fly? Repeat for the other pressures listed in the table below and record your results.
   
   To print this page, select the File button at the top of your browser, them select the Print option.
   
   

   Pressure (psi)	25	50	75	100	125
   Height (feet)

   Note: The cone weight, body weight and tail weight also affect the height of a rocket, but you want to keep these constant so you can see the effect of pressure.
   
   
2. As you increase the pressure, keeping the volume constant, what happens to the number of gas molecules (the amount of gas) in the bottle and how does that explain the height the rocket reaches?
   
   
3. If you could pressurize the rocket to 25 psi and then increase the temperature, how would the increase of temperature affect the height the rocket reaches?

Additional Activities

1. You can make a graph showing how the height (y-axis) varies with increasing pressure (x-axis).
   
   
2. You can design and carry out an experiment to determine the effect of the amount of water in the rocket on the height of the flight. Keep pressure and all other variables constant. What is the optimum amount of water in the rocket?
   
   
3. You can make a graph showing how the height (y-axis) varies with the volume of air in the rocket (x-axis). Note: The volume of air is found by subtracting the water volume from 64 ounces — the total volume of the bottle.