Download balanced forces flight

Free body diagrams (Free body diagrams)
http://www.grc.nasa.gov/WWW/K-12/airplane/newton.html
1. An F18 Hornet aircraft sits motionless on a runway because of inertia. If that plane starts to
move down the runway, it means that there must be a force acting on it. Of the four main forces
that act on aircraft, which one is most likely to cause the forward motion down the runway?
2. Which of the four forces causes the airplane to become airborne?
3. Once the F18 Hornet is airborne, which force is equal to the force of thrust?
4. As the F18 Hornet travels at constant velocity, it burns fuel, which decreases its weight. In
response to this decrease, which of the four forces is also likely to decrease?
5. On the arrow above, indicate thrust force of the F18 Hornet pictured above:
6. On the arrow above, indicate lift force of the F18 Hornet pictured above:
7. On the arrow above, indicate weight force of the F18 Hornet pictured above:
8. On the arrow above, indicate drag force of the F18 Hornet pictured above:
9. Which one word defines Newton's First Law of Motion?
Consider the situations below to determine whether or not there is an external force acting on the
airplane. Remember that according to Newton's First Law, a plane will resist a change in its state
of rest or motion unless it is acted on by a force. Write the word force next to the situations
where an external force acts. You may ignore the effects of air resistance.
____________ 1. The F18 is flying at 200 mph at an elevation of 30,000 ft.
____________2. The F18 turns northeast at 200 mph and an elevation of 30,000 ft.
____________3. The F18 increases its speed to 220 mph at the same elevation.
____________4. The F18 continues flying at 220 mph at 30,000 ft.
____________5. The F18 drops to an elevation of 28,000 ft.
____________6. The F18 heads due east maintaining its speed and elevation.
Beginner's Guide to Aerodynamics
Cruising Aircraft and Balanced Forces Activity
http://www.grc.nasa.gov/WWW/K-12/BGA/Tonya_Dyke/BalancedForces_act.htm
If so instructed by your teacher, print out a worksheet page for these problems.
Open the slides called Airplane Cruise-Balanced Forces, Forces on an Airplane, and Aircraft MotionUnbalanced Forces (with text). Read the explanations on the four forces on an airplane and what happens
when the forces are balanced or unbalanced.
1. Define force.
2. What are the four forces acting on an airplane?
3. How do each of the four forces act on an airplane in flight? (Which direction does each force push or
pull on the airplane in flight?)
4. Define balanced and unbalanced.
5. In terms of the four forces acting on an airplane, what needs to happen so the forces are balanced?
What do we call it when all four forces are balanced on an airplane?
6. You are traveling on an airplane and the pilot announces on the intercom that you have reached
your cruising altitude of 32,000 feet. Explain what the pilot is telling you. (Include what is happening
with the four forces on the airplane).
7. During a flight when we are cruising at a specific altitude, the four forces are balanced. At which
points during a flight are the forces unbalanced?
8. Define Newton's First Law of Motion.
9. In your own words, explain how Newton's First Law of Motion explains the motion of a cruising
airplane.
10. What are some ways the forces on an airplane can become unbalanced? (Name at least three).
Beginner's Guide to Aerodynamics
Forces on an Airplane and Resulting Motion Activity
http://www.grc.nasa.gov/WWW/K-12/BGA/Michele_Kotick/ForcesonPlane_act.htm
If so instructed by your teacher, print out a worksheet page for these problems.
Open the slide called Forces on an Airplane (with text). Study the labeled diagram and read the explanation.
Next, open the slide called Simple Aircraft Motion and study the chart.
A. Answer the following questions.
(1) Which force on an airplane is always directed toward the center of the earth?
(2) Which force on an airplane can also be called a resistance force?
(3) Which force is responsible for moving the airplane forward?
(4) Which force do the wings of the airplane generate?
B. For questions 5-8, predict what effect the following flight conditions would have on the plane. (Would the
plane rise, fall, slow, or accelerate?)
(5) Drag > Thrust
(6) Lift > Weight
(7) Thrust > Drag
(8) Weight > Lift
The First and Second Laws of Motion
Newton's First Law of Motion states that a body at rest will remain at rest unless an outside force acts on it, and
a body in motion at a constant velocity will remain in motion in a straight line unless acted upon by an outside
force.
If a body experiences an acceleration (or deceleration) or a change in direction of motion, it must have an outside force
acting on it. Outside forces are sometimes called net forces or unbalanced forces.
The property that a body has that resists motion if at rest, or resists speeding or slowing up, if in motion, is called
inertia. Inertia is proportional to a body's mass, or the amount of matter that a body has. The more mass a body has, the
more inertia it has.
The Second Law of Motion states that if an unbalanced force acts on a body, that body will experience
acceleration ( or deceleration), that is, a change of speed. One can say that a body at rest is considered to have zero
speed, ( a constant speed). So any force that causes a body to move is an unbalanced force. Also, any force, such as
friction, or gravity, that causes a body to slow down or speed up, is an unbalanced force. This law can be shown by the
following formula
F= ma



F is the unbalanced force
m is the object's mass
a is the acceleration that the force causes
If the units of force are in newtons, then the units of mass are kilograms and the units of acceleration are m/s 2. If the
units of force are in pounds (English), then the units of mass are in slugs, and the units of acceleration are ft/s 2.
Motion of an object that is not accelerated (moving at a constant speed and in a straight line) can be found using the
formula
d= v t



d is the distance traveled
v is the rate of motion (velocity)
t is the time
Some sample problems that illustrates the first and second laws of motion are shown below:
Example 1
If the speed of sound on a particular day is 343 m/s, and an echo takes 2.5 seconds to return from a cliff far away, can
you determine how far the cliff is from the person making the sound?
An echo is a sound that travels out and back. It take 2.5 seconds for this trip, which is twice the distance to the cliff.
Therefore, it only takes 1.25 seconds for the sound to reach the cliff. By substitution,
d=vt
d = (343 m/s) (1.25 s)
d = 429 m
Example 2
If an unbalanced force of 600 newtons acts on a body to accelerate it at +15 m/s2, what is the mass
of the body?
F = ma
m=F/a
m = 600n/15 m/s2
m= 40 kg
Excersices:
1. If a car is traveling at 50 km/hr along a straight line, how many meters does it travel in 10
seconds?
(Answer)
2. A force of 5000 newtons is applied to a 1200 kg car at rest. What is its acceleration?
(Answer)
3. 10 kg body has an acceleration of 2 m/s2. Find the net force acting on the body.
(Answer)
4. An empty truck with a mass of 2500 kg has an engine that will accelerate at a rate of 1.5 m/s2.
What will be the acceleration when the truck has an additional load of 1500 kg ?
(Answer)
5. A box resting on a table has a mass of 5.0 kg.
a. What is its weight?
b. What will be its acceleration when an unbalanced horizontal force of 40 newtons acts
on it?
(Answer)
6. What is the weight of an object that has a mass of 60 slugs?
(Answer)
7. A net force of 75 pounds acts on a body of 25 slugs. The body is initially at rest. What is its
acceleration during the action of the force?
(Answer)
8. What is the mass of a 185 pound man? If a 100 pound horizontal net force acts on the man while
he is sitting on a wooden floor, what will his acceleration be?
(Answer)
http://www.grc.nasa.gov/WWW/K-12/BGA/Sheri/newton's_second_law_act.htm
On December 17,1903, at Kill Devil Hill, North Carolina, the Wright brothers made the first sustained,
controlled powered flight. Their airplane weighed about 700 lbs.
Use the information shown below to answer the questions.
Force ( Newtons) = mass (kilograms) x acceleration (meters/second) where acceleration due to gravity (g) =
9.80 m/s2, 1 kg = 2.205 pounds, and 1 foot = 0.3048 meters.
1. Write a formula that can be used to calculate the force due to weight.
2. Convert the mass of the airplane into kilograms.
3. Now calculate the force due to weight on the Wright brothers' airplane.
4. In order for their airplane to fly, the lift force must have exceeded: _______.
5. The Wright Brothers' airplane flew 120 feet in 12 seconds. Calculate its speed in feet per second.
6. Convert this speed to meters/second.
7. If Orville had gained 5 kilograms before the flight, calculate what the lift force would have been.
8. If the Wright brothers' airplane had weighed only 675 pounds, what would the lift force have been?
9. A Boeing 747 has a mass of 1,764,000 kg. What is the lift force required to get it off the ground?
10. A Boeing 727 has a mass of 396,900 kg. What is the lift force required to get it off the ground?