Motion I. What is motion? (How do you know you moved?) a. II. Why study motion? (What happens if there isn’t motion?) a. Everything in the universe is moving b. c. Foundation of physics III. What is needed to determine that a change in position took place? a. Coordinate axes i. Defines origin/start/zero point ii. Used to show position: (x,y) iii. In physics negative does not mean a number is smaller than zero 1) 2) Example a. IV. Frame of reference a. Point of view affects how motion is seen b. Tossing ball demo i. Whose frame of reference is right? 1) 2) Newton and Einstein – There is no special place a. c. How can more than one frame of reference be correct? i. The statement I am right and you are wrong implies a special place where the laws of physics behave differently ii. The laws of physics work everywhere d. Inertial Vs. Non-inertial Frame of Reference i. Inertial – frame of reference that is moving at a _____________________________. 1) The motion of an object in this frame of reference to be described without the presence of “fictitious” forces. 2) Example - While driving down the road at a constant velocity your friend in the passenger seat throws a ball straight up. The ball falls back down into your friend’s hand. ii. Non-inertial – does not have a constant velocity, therefore it is _________________. 1) An object whose position is judged from this frame will seem to spontaneously change its velocity with no apparent non-zero net force acting upon it. 2) When do we have a non-inertial frame of reference? a. b. c. 3) Example - If you are in an automobile when the brakes are abruptly applied, then you will feel pushed toward the front of the car. There is really no force pushing you forward. V. Relative Motion a. Motion in more than one frame of reference b. All motion is relative to an observer i. What is observed depends on the observer’s frame of reference c. Relative motion demo with constant speed car and wireless camera i. Let the car represent a boat on the river traveling at a speed equal to the current 1) What is the speed of the boat relative to the boat or the current? a. 2) What is the speed of the boat moving with the current relative to an observer on land? a. 3) What is the speed of the boat moving against the current relative to an observer on land? a. 4) What other way could the moving boat have a relative speed of 0m/s relative to an observer on land? a. b. Example i. d. Relative velocity video e. Where else is relative motion experienced in real life? i. ii. iii. f. Solving for relative motion mathematically i. Writing relative velocities mathematically – relative velocity of an object to another can be written algebraically. 1) Relative velocity of object A to object B is ________ 2) When you change the frame of reference you need to change the sign. a. Example: A ball is rolling on the ground to the right with a velocity of 3 m/s. i. The velocity of the ball to the ground, Vbg, is ________. ii. The velocity of the ground to the ball, Vgb, is ________ ii. The velocity of object A to object C is equal to the velocity of object A to object B plus the velocity of object B to object C. 1) a. The subscript “b” cancels out in the equation. VI. Is there an experiment that can be done to prove that you are moving with constant velocity? a. Thought experiment i. You fall asleep and wake up in a room with one window. Looking out that window all you see is blackness, except for an object in the distance. You notice the object in the distance is getting closer? 1) Are you or the object moving? a. b. b. Examples i. While sitting in a parked car, the car beside you backs up 1) If you didn’t know the car beside you was backing up, your frame of reference thinks it is moving __________________ ii. While standing on the shore line the ocean water retreats back to the ocean 1) Your frame of reference might think it is moving ___________________ iii. Driving parallel to a parked train 1) The train appears to be moving VII. Scalars a. Number that shows magnitude (size) only b. Just add c. Do not have to consider direction VIII. Distance (Scalar) a. Measures how far b. Total distance of the path followed by the moving object c. Do not have to consider direction d. Example i. Car’s odometer reading ii. New York City is 2400 miles away from Los Angeles iii. What distance have I traveled, if I walk from NYC to LA and back? 1) IX. Vectors a. Arrow that shows magnitude (size) and direction b. Must consider direction before adding c. Used to analyze motion d. Vectors must be written with ____________________ and _____________________ e. An arrow may be placed above a variable to represent a vector: X. Position (Vector) a. Where an object is located relative to a selected origin b. Need magnitude and direction c. Example i. XI. Displacement (Vector) a. Measures how far b. Straight line distance from where an object started (di) to where it ended (df) c. Example i. What displacement have I traveled, if I walk from NYC to LA and back? 1) XII. What is the difference between distance and displacement if both measure how far? a. XIII. How quickly is positioned changed? a) Refer to toy car lab b) What must we measure to prove this? 1) Set distance and measure time 2) Set time and measure distance how far c) how fast howlong XIV. Speed (Scalar) a. Measures how fast b. Not dependent on direction c. Average Speed = Total Distance / Time d d. v t e. Example i. What is my average speed if I walk from NY to CA and back in 600 hours (25 days)? 1) XV. Velocity (Vector) a. Measures how fast b. Dependent on direction c. Average Velocity = Displacement / Time d d. v t e. Example i. What is my average velocity if I walk from NY to CA and back in 600 hours (25 days)? 1) XVI. What is the difference between speed and velocity if both measure how fast? a. Measures? Variable Scalar Vector Displacement - Straight line Total Distance How far? d distance from start to finish Direction not Important Direction is Important How fast? v d Distance Displacement Equation v Speed Velocity t Time Time XVII. Instantaneous versus average a. Instantaneous i. b. Average i. c. Show motorcycle speedometer video i. The motorcycle goes from an instantaneous speed of 0.0km/hr to an instantaneous speed of 300km/hr (190mph). What is the motorcycle’s average speed? 1) .