Download Activity 4.2.2 Airfoils, Lift and Bernoulli`s Principle

Activity 4.2.2 Newton’s Laws of Motion
Introduction
Aerospace design engineers use aerodynamics, the science of motion of air and
forces acting on bodies in air, to design airplanes that will fly. One of the jobs of an
aerospace engineer is to create wing shapes that produce lift as the air moves over
the wings. If an airplane is going to fly, the amount of lift must be greater than the
force of gravity, and the amount of thrust produced by the engine must be greater
than the drag force created by air resistance. Wing shapes that provide lift and have
the proper angle of attack (the angle at which a wing meets the flow of air) can then
help an airplane overcome gravity. Research has shown that a wing with a
streamlined shape can overcome drag with the thrust of engines. The less drag on
an airplane, the less power it needs to move.
In this activity you will learn the basic concepts of aerodynamics, including basic
definitions, Newton’s laws of motion, and forces acting on an airplane during flight,
and in the next activity, Bernoulli’s principle, which is the major contributor to lift.
Knowledge of these science concepts will help you as you investigate atmospheric
flight and space flight later in this unit.
Equipment
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Gateway notebook
Pencil
3 dragsters with different mass (or one dragster capable of changing mass)
Dragster track
Dragster manifold and compressor
Calculator
Stopwatch
2 L bottles
Water bottle rocket launcher
Method for measuring height of water bottle rocket launch
Procedure
Answer the questions below as your teacher guides you through several activities.
Discovery of Forces – Newton’s First Law
Watch your teacher’s demonstration to answer the questions below.
1. Describe the action of the two blocks as your teacher demonstrates Newton’s
first law of motion.
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2. Read the statement below and explain why you agree or disagree with the
statement. Give an example.
An object at rest will remain at rest unless acted on by an unbalanced force. An
object in motion continues in motion with the same speed and in the same direction
unless acted upon by an unbalanced force.
Changes in Force – Newton’s Second Law
Think about riding a skateboard. If you push off lightly, will you travel very far? What
if you push off harder? When you push off, you are applying a force to an object with
mass (that would be you), and when you put yourself into motion, you are
accelerating. Think about this while completing the following experiment.
Several students will time how long it takes for a dragster to travel the length of the
track when different forces are applied to the dragster. Read all directions before you
begin.
1. Make a prediction in the space below on how you think a dragster will accelerate
down the track using different amounts of force. Determine who in your group will
time the activity and who will record information for this activity. Use the supplied
data table to record your information.
2. Your instructor will set a dragster on the track and tell you the mass of the
dragster. Record the mass in the correct location in the data table.
3. You will run the dragster a total of 9 times – 3 times at each specified amount of
force. Your instructor will set the force levels on the compressor.
 3 runs with a force of 40 psi
 3 runs with a force of 60 psi
 3 runs with a force of 80 psi
4. Record the time and distance traveled for each run. Note: the run time is the time
from the launch (3-2-1-LAUNCH!) until the dragster hits the end of the track or
comes to a complete stop.
5. Use your data to calculate the average velocity (speed) of the dragster for each
force used. Speed = distance ÷ time
6. Use the calculated velocity (speed) and the time to determine the acceleration.
Acceleration = velocity ÷ time
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Technically, acceleration is defined as the change in velocity divided by the change
in time. Acceleration = (final velocity - starting velocity) ÷ (final time - starting time)
However, since our starting velocity and starting time are both zero, we are able to
shorten the equation as shown above.
7. Complete the data table for changes in force.
Mass of the dragster _______________________ grams
Force
Distance
Time
Average Velocity
(distance/time)
Acceleration
(velocity /time)
Average
Acceleration
40 psi
40 psi
40 psi
60 psi
60 psi
60 psi
80 psi
80 psi
80 psi
Changes in Mass – Newton’s Second Law
Think about pushing a shopping cart. When the cart is empty, it is easy to start
moving, easy to keep moving, and easy to stop. However, when the cart is full, it
becomes much more difficult to start and stop. Keep this in mind as you complete
the following lab.
1. Make a prediction in the space below regarding how you think dragsters of
different masses will accelerate down the track if the amount of force stays the
same.
2. Determine who in your group will time for this activity and who will record
information for this activity. Use the supplied data table to record your
information.
3. Your instructor will set a dragster on the track and tell you the force being used.
Record the force in the correct location in the data table.
4. You will run the dragster 9 times – 3 times with each dragster of a different mass.
Your instructor will set the force levels on the compressor.
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5. Record the time and distance traveled for each run. Note: the run time is the time
from the launch (3-2-1-LAUNCH!) until the dragster hits the end of the track or
comes to a complete stop.
6. Use your data to calculate the average velocity (speed) of the dragster for each
force used. Speed = distance ÷ time
7. Use the calculated velocity (speed) and the time to determine the acceleration.
Acceleration = velocity ÷ time
Technically, acceleration is defined as the change in velocity divided by the change
in time. Acceleration = (final velocity - starting velocity) ÷ (final time - starting time)
However, since our starting velocity and starting time are both zero, we are able to
shorten the equation as shown above.
8. Complete the data table for changes in mass.
Constant air pressure: ___________________ psi
Mass
Distance
Time
Average Velocity
(distance/time)
Acceleration
(velocity /time)
Average
Acceleration
Conclusions
1. If the mass remains constant and the force changes, what happens to the
acceleration?
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2. If the force remains constant and the mass changes, what happens to the
acceleration?
3. Were some of your results inconsistent with the rest of the data? If so, why do
you think the experiment produced unexpected results?
4. Newton’s second law says that force and acceleration are directly proportional,
meaning that if the force is increased three times, the acceleration should
increase three times. Did this occur in your lab? If not, why do you think it didn’t
happen?
5. What effect does resistance have on the acceleration of the dragsters? Be sure
to discuss both air and friction.
6. Read the statement below and explain why you agree or disagree with the
statement. Give an example.
Acceleration is produced when a force acts on a mass. The greater the mass of the
object being accelerated, the greater the amount of force needed to accelerate the
object. Therefore, Force = mass x acceleration or F = ma.
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Reaction of Forces – Newton’s Laws
Newton’s third law states that
For every action there is an equal and opposite reaction.
This means that for every force, a reaction force exists that is equal in size but
opposite in direction. Whenever an object pushes another object, it gets pushed
back in the opposite direction equally.
For this activity each team will create and launch a bottle rocket. Your team will
determine the optimum amount of water for maximum rocket height. You will
determine the altitude of the rocket when launched using the method prescribed by
your instructor.
Compressed air is air stored at a higher pressure than atmospheric pressure.
Energy contained in compressed air is called potential energy because it is energy
that is available for use. It has the potential to be turned into action energy, also
called kinetic energy. Once all of the potential energy is used up (meaning the air
has reduced in pressure to that of the unconfined surrounding air), the air will not
push anymore. Think about how this may apply in the activity you are about to
complete.
To begin, let’s investigate the relationship between the amount of water in the bottle
and the distance that a rocket can fly.
1. Individually use the following website to simulate a water rocket:
http://www.grc.nasa.gov/WWW/K-12/bottlerocket/br2d_b.swf
2. Make a prediction on the effect the amount of water in the bottle has on the
distance the rocket will travel.
3. Run the simulation software using the 2 liter bottle. You may choose to either use
or omit the nose cone, but once you make the decision, you must run all of the
tests the same way (with or without the nose cone).
4. Changing only the amount of water in the rocket, run the simulation five times
and record the data in the table below.
Trial
% Water in the Bottle
Meters Traveled
Maximum Velocity
1
2
3
4
5
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5. Share your results with the class based on the options you chose.
You will now be divided into teams. Each team will decide on a specific amount of
water (in milliliters) to place in the bottle. Use the procedure described below.
6. Fill the bottle to the desired amount.
7. Pour the amount into the graduated cylinder. Report the volume you intend to
use to your instructor.
8. Your instructor will explain the method to be used for determining altitude
The following jobs must be covered by the members of the team.
 Prep/Launch/Recovery - Responsible for preparing the rocket for launch,
checking the rocket to make sure it is flight ready, and filling it with the right
amount of water. Responsible for mounting the rocket, pressuring the rocket,
and launching it skyward. Also responsible for retrieving the rocket after
launch.
 Measurement – Responsible for determining the height the rocket traveled.
Responsible for tying fishing line on to the neck of the rocket. When fishing
line is payed out during launch, team member is responsible for measuring
the length of the line.
 Spotter - Responsible working with the Measurement team member to
determine the height of the rocket.
 Recorder - Responsible for entering all pertinent data for each flight.
9. All launches will be conducted with the same air pressure in the rockets.
10. After the rocket is launched, the spotters should communicate the peak altitude
to the recorder team to be placed on the data table.
The recorders should position themselves with the Measurement and Spotter team
members prior to launch. The recorders will record the altitude estimates from the
spotters as they are made. Data will be collected from each launch. The recorders
will share the results with the rest of the team members. Data will be collected from
all teams’ launches.
ml Water
Altitude
ml Water
Altitude
ml Water
Altitude
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Average the altitudes of the trials where the same amount of water was used. Place the
averages in the table below. Write your results from the lowest altitude to the highest
altitude.
Conclusions
1. Restate your prediction. Did the test data support your prediction? If so, explain
how. If not, give possible reasons why not.
In the first stage of the rocket’s flight, the rocket was sitting on the launch pad. In the
second stage of the rocket’s flight, air was added to increase the pressure of the
water in the water bottle rocket (i.e., potential energy) in order to make the rocket fly
to a certain altitude. The third stage of flight was the actual launch.
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2. Fill in the table below, explaining how Newton’s three laws of motion are in use
during each stage of the rocket’s flight. Also discuss the conversion of energy at
each stage.
Newton’s 1st
Law of Motion
Newton’s 2nd
Law of Motion
Newton’s 3rd
Law of Motion
Energy
1st Stage of
Flight
2nd Stage of
Flight
3rd Stage of
Flight
3. Would the use of compressed air and water be practical in lifting rockets into
outer space? Why or why not?
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