Section 1 EO M140.01 – LAUNCH A WATER ROCKET
Resources needed for the delivery of this lesson are listed in the lesson specification located in A-CR-CCP-801/PG-001Proficiency Level One Qualification Standard and Plan, Chapter 4. Specific uses for said resources are identified throughout the instructional guide within the TP for which they are required.
Review the lesson content and become familiar with the material prior to delivering the lesson.
Photocopy and prepare Water Rocket Launch System; see instructions located at Attachment A, if required.
Prepare a Water Rocket launch site; see instructions located at Attachment B.
Practice assembling the Water Rocket launch System and launching water rockets before this lesson.
Water Rocket Safety Orders are located at Attachment C.
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An interactive lecture was chosen for TP 1 to orient the cadets to Newton’s Laws of Motion.
An in-class activity was chosen for TP 2 as a fun way to have the cadets launch a water rocket in a safe and controlled environment.
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By the end of this lesson the cadet will have launched a water rocket.
This lesson will demonstrate for the cadets Newton’s Laws of Motion and they will this in action when they launch a water rocket.
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Teaching point 1
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Explain and Discuss Newton’s Three Laws of Motion.
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Time: 15 min
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Method: Interactive Lecture
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Newton’s Laws of Motion
The three laws of motion were first compiled by Sir Isaac Newton in his work Philosophiæ Naturalis Principia Mathematica, first published on July 5, 1687. Newton used them to explain and investigate the motion of many physical objects and systems.
Newton's laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. A force can be defined as a push or a pull on an object.
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Demonstrate force by pushing and pulling an object (book, pen, etc.) in a straight line across a flat surface. |
Newton’s First Law of Motion, or the Law of Inertia.
Newton's first law states that every object remains at rest or in uniform motion in a straight line until an external or internal force is applied to the object. This is also the definition of inertia.
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion.
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Point to a movable object at rest. The object is following Newton’s First Law of Motion. |
If there is no force acting on an object then the object maintains a constant velocity. If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity changes because of the external force.
Constant velocity can only happen in a vacuum like space. On Earth, air and / or gravity creates resistance or friction, slowing the object down.
This first law gives a frame of reference for the other laws of motion by establishing that an object at rest or in motion can have its state of rest or motion altered by external or internal forces.
Examples of this Law are:
The pen placed on a flat level desk will not move as the forces of friction and gravity are acting on it.
A satellite in outer space continues on its trajectory unless the gravity of an object it passes alters its trajectory.
The Water Rocket on the Launch Tower will not move (other than a slight wobble due to air resistance from wind) as gravity keeps it on the launch tower until it is pressurized and launched.
Newton’s Second Law of Motion
Newton's second law of motion explains how an object changes velocity if external forces are applied to it.
1.The law states that if a force is applied to an object, it accelerates or changes its velocity, and it changes its velocity in the direction of the force.
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An object accelerates in the direction that the force is applied. |
2.The acceleration is directly proportional to the force applied. If an object is pushed, it causes it to accelerate. If the object is pushed three times harder, the acceleration is three times greater.
3.The acceleration is inversely proportional to the mass of the object. If two objects are pushed equally, and one of the objects has five times more mass than the other, it accelerates at one fifth the acceleration of the other.
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If the mass of an object increases, the acceleration decreases proportionately. |
Some of the forces that can change an objects state are:
gravity,
air resistance,
friction,
external or internal force.
A formula to help explain this is:
F=ma
Where F is equal to the force, measured in Newton Metres and m is equal to the mass of the object. A is equal to the acceleration of the object.
Rockets during launch burn some of their propellant and therefore become lighter, changing their mass. As the rocket mass changes or becomes lighter, and the rocket engine continues to produce the same amount of thrust, the rocket accelerates.
Newton’s Third Law of Motion
Newton’s Third Law of Motion states that for every action or force in nature there is an equal and opposite reaction. This force is proportionate to the mass of the objects involved
When the trigger is pulled on a firearm, the gunpowder explodes, pushing the projectile or bullet out of the barrel. The force applied to the projectile is the same as the force applied to the firearm. The mass of the firearm is less than the mass of the projectile resulting in less force applied to the shooter.
A rocket engine forces gasses or propellant out its nozzle, pushing the rocket in the opposite direction.
What is Newton’s First Law of Motion?
What is Newton’s Second Law of Motion?
What is Newton’s Third Law of Motion?
Newton's first law states that every object remains at rest or in uniform motion in a straight line until an external or internal force is applied to the object.
Newton's second law of motion explains how an object changes velocity if it is pushed or pulled upon.
Newton’s Third Law of Motion states that for every action or force in nature there is an equal and opposite reaction.
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Teaching point 2
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Have the cadets launch a water rocket.
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Time: 65 min
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Method: In-Class Activity
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The objective of this activity is to demonstrate Newton’s Laws of Motion in a dynamic and interesting way.
An outdoor area 10 by 20 square metres,
A water rocket launch system,
A pump to supply compressed air to the launch system (a bicycle pump or tire inflator is best)
A two litre soda bottle in good condition (no deep scratches or obvious defects). Only use carbonated drink type bottles. Water bottles are not strong enough to be used on a pressurized system,
Safety glasses one per cadet instructors, and
Water to launch the water rocket several times.
Setup the launch site using the instructions included in Attachment B.
Brief the cadets as per Attachment B Launch Site Setup.
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For both launches use the same air pressure, 50 to 60 Psi. For the first launch, load the 2 litre soda bottle onto the launch system without water in it to demonstrate thrust with air as the propellant mass. |
1.Mount the empty two-litre soda bottle on the water rocket launch tower.
2.Explain to the cadets that the bottle is demonstrating Newton’s First Law of Motion as it is stationary and the only force currently applied is gravity.
3.Pressurize the launch tower to 50 to 60 psi.
4.Have the cadets count down from five and launch the soda bottle.
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The force of the air escaping from the soda bottle pushes the bottle into the air. This demonstrates two of Newton’s Laws of Motion. The First Law of Motion is demonstrated as the rocket is at rest on the tower. The Second Law of Motion is demonstrated as the rocket lifts off. The force of the air escaping pushes the bottle in a linear direction off the launch tower. The Third Law of Motion is demonstrated as the reaction of the air being pushed out of the bottle forces it away from the launch tower. |
5.Recover the soda bottle and fill it one third full with water.
6.Reload the soda bottle onto the launch tower.
7.Pressurize the launch tower to the same pressure as the empty bottle launch.
8.Have the cadets count down from five and launch the water rocket.
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For the second launch, load the two litre soda bottle onto the launch system after filling it one third full with water to demonstrate thrust with water as the part of the propellant. The mass of the bottle with the water in it slows the rocket down on launch, but the mass of the water being forced out of the bottle pushes the bottle much higher. As the bottle gets lighter, it accelerates faster until the propellant and pressure diminish. Even after the water has evacuated the bottle, the air pressure left in the bottle continues to provide thrust to the bottle until it is exhausted. |
9.Have the cadets discuss the difference between the two launches.
Water Rocket Safety Orders are located at Attachment C.
The cadets’ participation in the activity will serve as the confirmation of this lesson.
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Newton’s Laws of Motion apply to everything around us. In rocketry, these laws govern the entire flight profile of a rocket before, during and after launch.
Cadets qualified as Advanced Aerospace may serve as assistant instructors.
The water rockets may be launched indoors in an area easy to clean up (eg, gymnasium floor) or out of doors in favourable weather.
C3-266 Science Toy Maker. (2008). Making (and using) an overhead water rocket launcher. Retrieved October 1, 2008, from http://www.sciencetoymaker.org/waterRocket/buildWaterRocketLauncher.htm
C3-291 Retter, Y. (2008). Water Rocket – Skewer Design. Retrieved November 21, 2008, from http://www.geocities.com/yoramretter/SkewerDesign-v02.html
C3-351 National Aeronautics and Space Administration. (2008). Adventures in Rocket Science. Retrieved October 27, 2011, from http://www.nasa.gov/pdf/265386main_Adventures_In_Rocket_Science.pdf
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