Teachers TryScience

http://www.youtube.com/watch?v=WPwOYauqBRM&feature=youtu.be

• Why do we have to use water, or do we?
• Will it fly without water?
• If a little water works well, will a lot of water work better?
• Will it fly best when it is totally full?
• What volume of water works best?

These questions can be answered by experimenting with various levels of water using a bottle with no modifications.

To get an exact amount of water tests should be run with various amounts of water on the final product.

The Big Idea

Newton's Laws

Tell Students:

Launching something as large as the space shuttle is a complex project. But scientists can send this huge vehicle into orbit partly because they understand the natural laws that describe how objects move. Scientists discovered these laws years ago. Yet the laws are still fundamental to every rocket launch, even the bottle rocket that you will launch in this lab. The same law that states how hitting a tennis ball makes it go faster also tells how rockets are launched. This law is Newton's third law of motion.

'Newton's third law of motion' states that for every action there is an equal and opposite reaction. Newton's third law also applies to rockets. A rocket gets its lift from the gases pushing out of its tail. The force of the rocket pushing on these gases is the action force. The gases exert an equal but opposite force on the rocket, which forces the rocket up, this is called the reaction force.

The rocket gases do not have to push against anything, such as the ground. The reaction force exists even in outer space, even if there is no air for the gasses to act on. When astronauts need to change a rocket's path slightly, they rely on the action of gases. A rocket expels gas in one direction creating a reaction force that pushes the rocket in the opposite direction. The rocket accelerates.

Activity 1: Water Bottle Design Challenge

Materials

• 6 identical empty soda bottles (all from the same brand of soda so that they are equivalent in shape, weight, etc.)
• 1 Air Compressor
• 1 permanent marker to mark off water levels
• 1 measuring tape for measuring flight distances
• 1 measuring cup marked off in mL

Procedures:

1. Mark each empty soda bottle with 6 water levels: 0, 100, 200, 300, 400, & 500 ml.
2. Fill each bottle to one of the 6 levels.
3. Place a rubber stopper into each bottle – be sure to push each stopper in the same amount.
4. Fill a containers with enough water to refill the bottles during the launch activity
5. Bring the students outside to an area with plenty of space (and away from any cars or windows). sure to bring extra water with you to refill the rockets.
6. Give 1 bottle rocket to each student.
7. Before launching, have the students predict which rocket will go the farthest and why.
8. To prepare for launch, insert the bottle into the launch pad adapter.
9. Place the rocket on the “launch pad” with the stopped end facing down.
10. Make sure everyone is clear of the launch path. Have a student from the first group pump air into the rocket until it takes off. **You may get wet**
11. When the rocket lands, have the students from that group take the measuring tape and measure the distance from the launch pad to the landing site and share the measurement with the rest of the class
12. Refill the bottles to the level of water that the farthest-traveling rocket had in it to begin with.

Ask Students:

• Why did the rocket that was full of water barely take off? It was too heavy or massive. This can be explained with Newton's first law of motion:

A body at rest tends to remain at rest and a body in motion tends to stay in motion.

• The rocket didn't have enough "oomph" (force) to make it take off. Why? There was not enough force for the relatively huge mass. The more mass it has, the less it will accelerate using the same force. This can be explained using Newton's second law of motion:

Force equals Mass times Acceleration

• Why did the water go one way and the rocket the other? There is an equal force in both directions. This can be explained by Newton's third law of motion:

For every action there is an equal but opposite reaction.

More Questions to consider:

· How high does it fly?

· Do fins help keep the rocket stable?

· Does a parachute help keep it aloft?

· How might a parachute work?