# Straw Rocket with Launcher with a Nod to Newton

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Straw Rocket with Launcher with a Nod to Newton
Newton notes based upon NASA STEM Liaison, Janet Raines, Stomp Rocket presentation for the Oakley STEM Center.

What makes things move? Who was the first scientist credited with exploring how things move?
Galileo studied what makes things move, exploring: falling objects gravity friction forces Galileo Galilei ( ) *Review vocabulary: Gravity-the force of attraction between any two objects due to their mass Friction-rubbing forces that act against the motion between two surfaces Forces-pushes and pulls

One scientist is known for the three physical laws he discovered
One scientist is known for the three physical laws he discovered. What is his name and what are his laws called? Sir Isaac Newton ( ) Newton explained Galileo’s discoveries with his three “Laws of Motion.”

Newton’s 1st Law Law of Inertia
An object at rest tends to stay at rest. An object in motion will stay in motion at a constant speed in a straight line unless acted on by a force. *Inertia is the resistance to changes in motion. Examples: bowling, crash dummies, golf Q: What would happen to the dummies if they didn’t have their seatbelts on? A: The crash test dummies would keep going, through the windshield. Q: How does the 1st law apply to the launching or flight of a rocket? A: The rocket will stay on the launch pad unless it is acted upon by a force. The rocket will continue to go the direction it is launched unless it is acted on by another force.

Newton’s 2nd Law Law of *Acceleration
F=ma Force = (*mass) x (acceleration) The more force on an object, the more it accelerates. The more massive an object is, the more it resists acceleration. Mass – the amount of matter in an object Velocity – speed and direction of a moving object Acceleration - change in velocity with respect to time Mass—the amount of matter in an object Velocity-speed and direction of a moving object (not included on this slide) Acceleration—change in velocity with respect to time Q: What if we pushed a go-cart (more mass) with the same amount of force that we used to push a toy car? Would it go faster or slower than the toy car? A: It would go slower, because it weighs more.

Newton’s 2nd Law and Rockets Law of Acceleration
The more force (*thrust) from the rocket engine, the greater the acceleration. The lighter the rocket, the greater its acceleration for a given thrust. Thrust—the force that pushes the rocket Q: Will the acceleration get larger or smaller if the Force is increased? A: The acceleration will be greater if there is a larger Force (acceleration is directly proportional to the Force). Q: What will happen to the acceleration if the mass is increased? A: The acceleration will be less if there is a greater mass (acceleration is inversely proportional to the mass). Q: Which requires a bigger rocket engine for launching into orbit, a GPS satellite weighing 34.8 thousand pounds, or the Space Shuttle, weighing 4.5 million pounds (including rocket boosters)? A: The space shuttle requires 3500 tons of thrust to launch. A typical GPS satellite is launched on a Delta II rocket, which is only capable of delivering up to 60 tons of thrust.

Newton’s 3rd Law Law of Action/Reaction
When one object exerts a force on a second object, the second object exerts an equal but opposite force on the first object. Q: What are some examples of this law? A: Answers will vary; a few examples are as follows: The sting you feel on your hands from hitting a baseball is the reaction of the ball hitting the bat. When you push off the ground on your scooter or skateboard, you move because the ground pushed back! When the space shuttle leaves the earth, it is pushed upwards by the opposite reaction of the thrust pushing against the earth.

What is a rocket? A rocket is a vehicle that is self-contained and self-propelled. It achieves motion from Newton’s principle of a reaction resulting from every action. The 3rd law is what moves rockets. In a space shuttle launch, you see the explosive gases shooting towards the earth, and the rocket moves in the opposite direction, off of the launch pad. In our rocket launch, the thrust of the air pressure pushes against our rocket, and the rocket pushes back with equal force, leaving the launch tube.

Forces Acting on a Rocket
* *Lift * Today we are going to build our rocket for maximum distance, so we also have to look at other forces in addition to gravity. Drag--a force that resists the rocket’s forward motion; caused by air molecules hitting the rocket. That is why rockets need to have an aerodynamic shape, and care needs to be taken to build it to eliminate drag. Drag works against thrust. Gravity-- the force that pulls the rocket towards the ground. If the rocket is unbalanced, the flight of the rocket will not be stable. Wind-- a force that can change the direction of the rocket when it is in flight. The rocket has to be able to resist the force of any wind that may blow it off course. For large rockets wind forces are often small and can be ignored. For small rockets, such as models, including our straw rockets, wind forces can be important. Thrust—the force pushing the rocket forward Lift – a force that acts on the rocket perpendicular to the control surfaces or “fins.” In an airplane these control surfaces would be the flaps and the plane flies due to the lift force acting on the wings. * *

Another View of Rocket Forces

How do Rockets demonstrate Newton’s 3 Laws of Motion?
1st Law: The rocket stays at rest until acted upon by a force. Once in motion, the rocket tends to stay in motion until acted upon by a force. 3rd Law: The thrust of the rocket fuel out of the rocket pushes it away from the Earth. Q: As a review, how does the launch and flight of a rocket illustrate each of Newton’s laws? A: The rocket doesn’t move unless it is acted on by a force. The amount of force necessary to move the rocket depends on its mass. The liftoff of a rocket is a reaction to the downward force of the thrust. 2nd Law: The greater the force exerted on the rocket, the greater its acceleration.

Building a Straw Rocket
We can explore how a rocket works with a simple model built from a straw Instead of engines that fire to create the thrust force… We will use a rubber band launcher to create the thrust force Get ready!

Materials Scissors Roll clear tape Rubber band Popsicle stick – large
Straw – generic (can be flexible) Ball of modeling clay 1 cm diameter Plastic coated paper clip Set of 2 fin templates

Fin Template

Cut the straw so that you remove the flexible portion with the shorter end.

Fold paper clip into launch lug
Unfold paper clip into “S” Shape. Fold ½ of the wide end of the “S” to form a 90° angle. Do NOT create or attach the launch lug if you are using the Pitsco Straw Rocket launcher.

Attach paper clip to straw ½ cm from end.
Wrap tape around straw and paper clip at top and bottom of paper clip. Do NOT create or attach the launch lug if you are using the Pitsco Straw Rocket launcher.

Press clay onto straw at launch lug end and form into a nose cone shape.
Be sure to press some of the clay into the straw so that you cannot shake it off easily.

Cut out and attach fins. Cut out both fins – they look like arrow heads. Wrap tape around straw at tip and shaft. (Tape should not intersect dotted lines.) Attach second fin in same way. Fold arrows at dotted lines to make 4 fins!

Create launcher. Stick a piece of tape parallel to and on the end of the popsicle stick. Place a rubber band on the tape at the tip of the popsicle stick. Fold the tape over and onto the popsicle stick. Place one more piece of tape on in the same way. Do NOT create this launcher if you are using the Pitsco Straw Rocket launcher. Wrap a piece of tape perpendicular to and around the popsicle stick.

Launch the rocket! Do NOT create this launcher if you are using the Pitsco Straw Rocket launcher. Hold the rocket parallel to the launcher. Hook the rocket to the rubber band using the launch lug. Make sure you are not aiming at anything alive or breakable. Pull the rocket back to stretch the rubber band tight. Let go of the rocket!

Discover the answers Does launch angle (the angle between horizontal and line of popsicle stick launcher) affect the distance your rocket flies? Does the amount of stretch you have in your rubber band affect the distance your rocket flies? Does the mass of the nose cone affect the flight distance? Can you predict how far the rocket will fly based upon angle of launch and length of stretch in rubber band?