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Published byMadeleine Burns Modified over 9 years ago
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Kinematics Review Kinematics Review a) Exam information
b) What kind of questions? c) Review
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First Midterm Exam on Friday
Covers Units 1-3 plus “Math” One-dimensional Kinematics Two-Dimensional Kinematics Relative and Circular Motion Unit conversion Trigonometry and Algebra 50 minute duration Multiple choice Calculators Allowed/Needed Three sheets of notes. (equivalent font size>9)(this is font size=9)
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What type of questions? Interpretation and use of graphs
Which of the following statements about the velocity of the cart is correct? What is the velocity at t=? What is the acceleration at t= ? ….
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What type of questions? Displacement, velocity and acceleration in 1 dimension Given some combination of acceleration, initial velocity, final velocity, displacement, elapsed time, etc. calculate an unknown quantity using the kinematic equations….
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What type of questions? Motion with constant acceleration in 1-dimension V0=0m/s ground H=10m V1 Given some combination of acceleration, initial velocity, final velocity, displacement, elapsed time, etc. calculate an unknown quantity using the kinematic equations….
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What type of questions? Relative motion in 2 dimensions
Given some combination of relative velocity between frames of reference answer questions related to the displacement and elapsed times for certain actions…
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What type of questions? Projectile motion
Given some combination of initial velocity, range , maximum height, etc…calculate characteristics of projectile motion..
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What type of questions? Circular Motion
Top view Given some combination of angular velocity, Radius, ac calculate a characteristic of the motion of an object at constant speed in a circle…
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What type of questions? Any material from Units 1-3 Calculations
Unit conversion Algebra, trigonometry and vectors Conceptual Questions Similar to pre-lecture and checkpoint questions
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What type of questions? Vectors q
Decompose a vector into polar or Cartesian coordinates Vector Addition (Subtraction)
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How to prepare? Read the textbook Review the video prelectures
Review the lecture slides (Re-)Work homework problems Prepare three sheets of notes Basic Fundamental Equations Derived Equations( and be able to derive them!) Unit conversions Algebra notes (quadratic equation) Trigonometric relations Vector concepts Conceptual notes,… Get enough sleep!!!
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Main Points of Unit 1
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Main Points of Unit 1
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Vectors and 2d-kinematics – Main Points
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Vectors and 2d-kinematics – Main Points
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Vectors and 2d-kinematics Important Equations
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Relative and Circular Motion
a) Relative motion b) Centripetal acceleration
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Hyperphysics Motion Displacement vs timet Velocity vs timet
Acceleration vs timet
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Hyperphysics Motion
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1d-Kinematic Equations for constant acceleration
Basic Equations to be used for 1d – kinematic problems. Need to apply to each object separately sometimes with time offset When acceleration changes from one constant value to another say a=0 The problem needs to be broken down into segments
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Maximum Height of ball thrown upward in gravitational field
What is the velocity of an object when it is at its maximum height? Two ways to solve for maximum height… Solve for time first Solve for position directly Remember a is negative Use tf to solve for maximum height…
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The meeting Problem Whenever possible solve symbolically.
Define your problem; Identify useful equations Whenever possible solve symbolically. Then plug in the numbers!!!! You can understand what is going on better if you keep the equations organized. Start solving… Gather terms…Does the equation look reasonable? Solve for desired quantity… Position of object 1 when object 2 is launched This time is w.r.t object 2. To obtain time w.r.t object 1 need to add delay time Speed of object 1 when object 2 is launched
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Break problem into parts
Region 1: 0<t<1.5 s Region 1 Region 2 Region 3 Region 2: 1.5s<t<3.0s What happened in region 3? Region 3: 3.0s<t<5.0s Smartphysics Conclusion
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2d-Vectors q Think of a vector as an arrow. (An object having both magnitude and direction) The object is the same no matter how we chose to describe it 25
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Algebra and Trigonometry
Algebra is “fair” Quadratic Equation Trigonometry
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Vector Addition Add Components!!! AddTail to Head 27
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Kinematics in 3D Note: 3 directions are independent, but share time. 28
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Projectile Motion Horizontal Vertical Boring 29
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Ballistic Projectile Motion Quantities
Initial velocity speed,angle Maximum Height of trajectory, h=ymax “Hang Time” Time of Flight, tf Range of trajectory, D Height of trajectory at arbitrary x,t
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Derived Projectile Trajectory Equations
Maximum height Time of Flight (“Hang Time”) Range of trajectory Height of trajectory as f(t) , y(t) Height of trajectory as f(x), y(x)
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Relative Motion in 2 Dimensions
Speed relative to shore
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Relative Motion in 2 Dimensions
Direction w.r.t shoreline
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Centripetal Acceleration
Constant speed in circular path Acceleration directed toward center of circle What is the magnitude of acceleration? Proportional to: Speed time rate of change of angle or angular velocity v = wR
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Additional Slides
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w is the rate at which the angle q changes:
v = wR w is the rate at which the angle q changes: q Once around: w = Dq / Dt = 2p / T v = Dx / Dt = 2pR / T
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v = wR Another way to see it: v dt =R dq dq R v = Rw
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Two thrown balls problem #2
Use your equation in symbolic form and gather the values to be used…. Solve for individual elements of equation…can check if things make sense Position of object 1 at moment object 2 is launched Velocity of object 1 at moment object 2 is launched Solve for displacement and relative velocity at time when object 2 launches Note that acceleration term after 2nd object is released drops out!!! Divide to obtain time when objects meet
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Homework Hints – Stadium Wall
Calculate time to reach wall using vx: Calculate y position at time to reach wall:
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Homework Hints – Stadium Wall
Calculate time to reach wall using vx: Calculate y position at time to reach wall:
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Homework Solutions-Baseball Stadium
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Plane Ride N E East of north
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Car on Curve
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Maximum Height of Trajectory
Height of trajectory,h=ymax
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Time of Flight, “Hang Time”
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Range of trajectory
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Angle for Maximum Range
MAXIMUM range OCCURS AT 450
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Height of Trajectory at time t or position x
Height of trajectory, y(t) Height of trajectory, y(x)
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Launch Velocity-Given R and
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Launch Angle
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Launch Velocity –Given R and h
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