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This seating arrangement allows for a 6-person group to sit together in a "pod" style setting. Perfect for group discussions or collaborative work.
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Reading Quiz #1:C1 and R1 Wednesday, 9/2/2015 PHYS 1003, Dr. Karen G. Andeen Marquette University
Question 1 (2 minutes) • A moped circles the Trevi Fountain in Rome at a constant speed of 40 kph. The moped’s velocity is also constant. • True • False
Question 1 (2 minutes) • A moped circles the Trevi Fountain in Rome at a constant speed of 40 kph. The moped’s velocity is also constant. • True • False Velocity is directional so since the moped is changing direction, the velocity is NOT constant.
Question 2 (2 minutes) • A hummingbird moves 20 cm backward in 0.5 s at a steady rate. The hummingbird’s speed is therefore -40 cm/s. • True • False
Question 2 (2 minutes) • A hummingbird moves 20 cm backward in 0.5 s at a steady rate. The hummingbird’s speed is therefore -40 cm/s. • True • False Speed is NOT directional so the hummingbird’s speed is 40 cm/s!
Question 3 (2 minutes) • In Chapter R1 different reference frames were discussed. The terms used were: • Standard Frame and Different Frame • Home Frame and Other Frame • Local Frame and Foreign Frame • Reference Frame and Alternate Frame
Question 3 (2 minutes) • In Chapter R1 different reference frames were discussed. The terms used were: • Standard Frame and Different Frame • Home Frame and Other Frame • Local Frame and Foreign Frame • Reference Frame and Alternate Frame
Volume R, Chapter 1 The Principle of Relativity
Where are you? • 238,900 mi from the moon • 4.367 light years from alpha centauri • ~3 m from me… • What do you notice? It’s all RELATIVE...you have to use the relationship to something for a distance to make sense.
Reference Frames • In the same way, we have to choose a reference frame to determine properties of the things we see around us…it’s all a matter of perspective.
Who is moving? https://www.youtube.com/watch?v=IwFzxxR-Hb4
Who is moving? https://www.youtube.com/watch?v=1-p0GUnfbYU
(Note, bullet trains can go >150 mph) How fast is the other train going? https://www.youtube.com/watch?v=tkYJuE15g5Q
R1T.1 • Which of the following are (at least nearly) inertial reference frames and which are not. Respond T if the frame is inertial and F if it is non-inertial Both answers might be right in some cases! • A non-rotating frame floating in deep space. • A rotating frame floating in deep space. • A non-rotating frame attached to the sun. • A frame attached to the surface of the earth. • A frame attached to a car moving at a constant velocity. • A frame attached to a roller-coaster car.
Inertial vs Non-inertial Reference Frames • Inertial Reference Frame has constant velocity. • Remember: no change in speed, no change in direction • Non-intertial reference frame has acceleration in one direction or another. • Note: Newton’s Law of Inertia states that “an object at rest stays at rest and an object in motion stays in motion unless acted on by another force…” Imagine a tennis ball hanging from a string in your car. You are the driver and you accelerate. From YOUR point of view—from YOUR reference frame—that ball appears to move without a force. BUT you’re in a non-inertial frame because you’re accelerating. From MY perspective on the street, the ball is “trying” to stay where it is…
Clarifying the Postulate of Relativity • What constitutes an EVENT? • Definite an occurrence at a specific point in space • Definite moment in time • How do we determine SPACETIME COORDINATES? • 4-vector: [t, x, y, z] • Origin: [0, 0, 0, 0] Motion in only one direction w.r.t. time: an (x,t) plot
R1T.2 • Which of the following physical occurrences fit the physical definition of an event? • The collision of two point particles • A point particle passing a given point in space • A firecracker explosion • A party at your dorm • A hurricane • A, B, and C • Any of the above could be an event, depending on the scale and precision of our reference frame.
R1T.2 • Which of the following physical occurrences fit the physical definition of an event? • The collision of two point particles • A point particle passing a given point in space • A firecracker explosion • A party at your dorm • A hurricane • A, B, and C • Any of the above could be an event, depending on the scale and precision of our reference frame.
R1T.3 • Since the laws of physics are the same in every inertial reference frame, there is no meaningful physical distinction between an inertial frame at rest and one moving at a constant velocity. • True • False
R1T.3 • Since the laws of physics are the same in every inertial reference frame, there is no meaningful physical distinction between an inertial frame at rest and one moving at a constant velocity. • True • False
R1T.4 • Since the laws of physics are the same in every reference frame, an object must have the same kinetic energy in all inertial reference frames. • True • False (Note: Kinetic Energy = ½ mv2)
R1T.4 • Since the laws of physics are the same in every reference frame, an object must have the same kinetic energy in all inertial reference frames. • True • False
R1T.5 • Since the laws of physics are the same in every inertial reference frame, an interaction between objects must be observed to conserve energy in every inertial reference frame. • True • False
R1T.5 • Since the laws of physics are the same in every inertial reference frame, an interaction between objects must be observed to conserve energy in every inertial reference frame. • True • False
R1T.6 • Since the laws of physics are the same in every inertial reference frame, if you perform identical experiments in two different inertial frames, you should get exactly the same results. • True • False
R1T.6 • Since the laws of physics are the same in every inertial reference frame, if you perform identical experiments in two different inertial frames, you should get exactly the same results. • True • False
Reference Frames • Multiple observers can witness and record the motion of the same object • Identifying the Observers • Home Frame (HF) and Other Frame (OF) • X-axes are parallel to one another • OF moves in +x direction as observed by HF • HF moves in –x direction as observed by OF
Reference Frames • Operational definition of frame MUST include how position and time will be determined. • How long does it take information to travel? • http://www.ebaumsworld.com/video/watch/81877766/
R1T.7 • Imagine two boats. One travels 3.4 m/s eastward relative to the earth and the other 5.0 m/s eastward relative to the earth. We set up a reference frame on each boat with the x-axis pointing eastward. Which boat should we select to be the Home Frame, according to the convention established in this chapter? • The faster boat is the Home Frame. • The slower boat is the Home Frame. • We are free to choose either boat to be the Home Frame.
R1T.7 • Imagine two boats. One travels 3.4 m/s eastward relative to the earth and the other 5.0 m/s eastward relative to the earth. We set up a reference frame on each boat with the x-axis pointing eastward. Which boat should we select to be the Home Frame, according to the convention established in this chapter? • The faster boat is the Home Frame. • The slower boat is the Home Frame. • We are free to choose either boat to be the Home Frame.
Newtonian Relativity • Standard orientation for spatial coordinate systems • x, y, z define the three spatial directions in HF • x’, y’, z’define the three spatial directions in OF • Common x axis in both frames • Time is absolute • Synchronized clocks will remain synchronized • t’ = t for all synchronized clocks • Describing motion in multiple frames • Need to know motion of OF w/r/t HF • β = boost = velocity of OF as measured by HF
Galilean Transformations • One frame of reference moves w.r.t. the other • coordinate axes are parallel • origins indicate observers • Describing the Motion Note: acceleration is frame independent for cases where the frames themselves are not accelerating: i.e. if it’s an inertial frame, A(t) = 0.