Transcript chapter 7 notes - School District of La Crosse

CHAPTER 7 NOTES
KONICHEK
I. Projectile motionA Projectile- this is the object
being launched
B. trajectory-The path the
projectile follows.
 II. Independence of motion in 2 dimensions

A. The horizontal motion of a object is
independent of the vertical motion.

1. A bullet shot and one dropped will strike
the ground at the same time if they are from the
same height.

a. The only force acting on the bullet
once outside the barrel of the gun is gravity.
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B. Equations to represent the motionneglect air resistance
1. X=VxT- this is horizontal
displacement
2. T2= 2Y/g -time for the
shot to hit the ground
EXAMPLE PROBLEM(P136)
 A stone thrown horizontally at 15m/s at
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from a cliff 44m high.
SINCE THE GROUND ID ZERO THE
OBJECT IS REPRESENTED BY A -44M
A)How long does it take to reach the
bottom?
B) how far from the base of the cliff does
the stone strike?
C) sketch the trajectory
SOLUTION
 A
 . T2= 2(height of cliff)/g
 T2=3(-44m)/9.8m/s2 = 3s
 B.
 X=Vt- 15m/(3s)=45m

DON’T WORRY THERES AN
EASIER WAY
C. Objects launched at an angle
1. The horizontal component is small since
no other forces are acting on it(Vcosθ)
2. Vertical components are larger at the
beginning
a. Object slows as it’s going up, at the top
it stops(Vsinθ)
b. the vertical component then increases
again but in the opposite sign when falling.
c. When the object reaches launch
height it is traveling at the same velocity as the
launch velocity
THESE WILL MAKE YOUR
LIFE EASIER 
 Magical projectile motion equations
 Rx= V2sin2θ/g
 H= -(vsinθ)2/2g
 T= -2Vsinθ/g
• 3. Sample problem - a ball in flight
has an initial velocity of 4.47m/s at
an angle of 66° above the horizontal.
Find
• A) How long it took the ball to land.
• B) How high the ball flew.
• C) Find the range
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III. Periodic motion-The motion of the
object repeats itself. A pendulum, a Yo Yo
A. circular motion-The product of 2
forces acting on an object.
1. F1- the outward force of inertiatangent to the motion of the object.
2. F2- the inward force called
centripetal force.
• F1 IS THAT IMAGINARY FORCE
F
• CALLED CENTRIFUGAL FORCE
1
F2
 B. Centripetal acceleration- This is the
acceleration towards the center of the circle

1. Ac= V2/r
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2. V= 2πr/T velocity for one time
period

3. Substituting into the equation a=
(2πr/t)2/ r  a=4π2r/T2

 C. Centripetal forces - the inward force
causing uniform circular motion

1 F= m( 4π2r/T2)
IV. Simple Harmonic Motion. _ when an
object is moved from an equilibrium position,
and is released, moves through an
equilibrium position.

A. Period- this is the time necessary for one
complete cycle.

B Pendulum- an object suspended on a
string which undergoes simple harmonic
motion.

1. Period of pendulum T= 2π√lg, so g=
4πl/T2