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What is Projectile Motion?. Instructional Objectives:. Students will be able to: Define Projectile Motion Distinguish between the different types of projectile motion Apply the concept to flying marble and measure its velocity TEKS 5.A and 5.B. Projectile Motion. - PowerPoint PPT Presentation
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Instructional Objectives:
• Students will be able to:– Define Projectile Motion– Distinguish between the different types of
projectile motion– Apply the concept to flying marble and
measure its velocity– TEKS 5.A and 5.B
Types of Projectile Motion
• Horizontal– Motion of a ball rolling freely along a
level surface– Horizontal velocity is ALWAYS
constant• Vertical
– Motion of a freely falling object– Force due to gravity– Vertical component of velocity
changes with time• Parabolic
– Path traced by an object accelerating only in the vertical direction while moving at constant horizontal velocity
Variables
Horizontal Vertical
Displacement a.k.a. distance
x (xf – xi) y (yf – yi)
Initial Velocity Vxi Vyi
Average Velocity Va Va
Final Velocity = Vxi Vyf
Time t t
Acceleration a g = 9.8 m/s2
Angle θ θ
Equations
• X- Component
• Y- Component
• Vectors
tvxx xiif
gtvv
ygvv
gttvyy
yiyf
yiyf
yiif
2
2
1
22
2
)sin(
)cos(
iyi
ixi
vv
vv
Note: g = 9.8 m/s2
(Acceleration due to gravity)
Factors Affecting Projectile Motion
• What two factors would affect projectile motion?
• Initial velocity
• Angle
Initial Velocity
Angle
Solving Problems Involving Projectile Motion
1. Read the problem carefully, and choose the object(s) you are going to analyze.
2. Draw a diagram.
3. Choose an origin and a coordinate system.
4. Decide on the time interval; this is the same in both directions, and includes only the time the object is moving with constant acceleration g.
5. Examine the x and y motions separately.
Solving Problems Involving Projectile Motion
6. List known and unknown quantities. Remember that vx never changes, and that vy = 0 at the highest point.
7. Plan how you will proceed. Use the appropriate equations; you may have to combine some of them.
Group Practice
• Interactive projectile motion calculator
http://library.thinkquest.org/10796/ch6/ch6.htm
• Other explanations and practice problems
http://tuhsphysics.ttsd.k12.or.us/Tutorial/Lessons/Projectile.htm#GenStrat
Class Exercise
An object is fired from the ground at 100 meters per second at an angle of 30 degrees with the horizontalCalculate the horizontal and vertical
components of the initial velocityAfter 2.0 seconds, how far has the object
traveled in the horizontal direction?How high is the object at this point?
Solution
• Part a
• Part b
• Part c
mssmtvx
t
xv
x
ix
1740.287
s
ms
mvv
sm
smvv
iiy
iix
5030sin100sin
8730cos100cos
0
0
222 0.28.9
2
10.250
2
1s
smss
mtgtvy iy
Summary of Concepts
• A projectile is any object upon which the only force is gravity,– For our purposes we will not consideration air resistance, so we will take the approach
all bodies fall at the same rate regardless of their mass
• Projectiles travel with a parabolic trajectory due to the influence of gravity,
• There are no horizontal forces acting upon projectiles and thus no horizontal acceleration,
• The horizontal velocity of a projectile is constant (a never changing in value),
• There is a vertical acceleration caused by gravity; its value is 9.8 m/s/s, down,
• The vertical velocity of a projectile changes by 9.8 m/s each second,• The horizontal motion of a projectile is independent of its vertical motion.
Labs
• CPO Manual
B-1: Launch Angle vs. Range
B-2: Launch Angle vs. Speed
B-3: Analysis of Range and Speed
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