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That the laws of physics must look the same to all observers that are not undergoing acceleration
Einstein: the laws of nature are the same in all inertial frames of reference

Principle of Relativity


That all non-accelerated observers will measure the same value for the speed of light
The speed of light is the same (equal to c) in all inertial frames of reference

Principle of the Constancy of the Speed of Light


2 principles that form the basis of special relativity

Principle of Relativity
Principle of the Constancy of the Speed of Light (strange)


The set of space coordinates and time in which an observer, at rest in that frame, conducts measurements

Frame of reference


A frame of reference that is not undergoing acceleration (i.e., one that is moving with constant velocity)

Initial frame of reference


How would someone in an airplane (moving at a constant velocity and in a straight horizontal line) know that they were moving if all of the windows were closed?

They cannot perceive this motion


Why would someone in an airplane (moving at a constant velocity and in a straight horizontal line) not perceive the motion that they were moving if all of the windows were closed?

Because the measurements done inside the plane cannot differentiate between being at rest and moving with constant velocity


Suppose the ship is going at 0.99c relative to ground and the person in the ship measures ten seconds. How much time does the person on ground measure?

tground = 71 s


One twin stays on earth and the other flies around in a space ship at speed V = 0.99999c. The one on the ship thinks that he’s gone from earth for 10 years. How much older is the twin who stayed on earth?

tground = 2236 yr


The length of a moving object is contracted along the direction of motion such that:
L = L0[1-(V/c)2]1/2
Here V is the relative speed between the two frames of reference. So the length measured on the moving frame is smaller than the length the object has in the frame in which it is at rest
There is no length contraction along directions that are perpendicular to the relative motion; only occurs in a direction parallel to the direction of relative motion
Increases as the relative speed increases

Lorentz contraction


Energy has mass (that is, that energy has inertia); conversely, it is a statement that mass (or inertia) has energy. And the proportionality constant between energy and mass is c^2.



A new type of field called a matter field exists in nature. Like EM fields, matter fields are quantized. For example, the matter field for electrons is allowed to posses enough energy for either 0 electrons, or 1 electron, or 2 electrons, and so on. Electrons (and other material particles) exist because matter fields are quantized in just these energy increments

The Quantum Theory of Matter


Sara is in a train moving north at 30 m/s. She throws a stone toward the front of the train at 10 m/s relative to herself. Chuck, standing beside the tracks, sees the stone move...

North at 40 m/s


A space ship a 10 m long flies by a stationary observer at a speed of 0.80c. How long does it appear to an observer on earth?

6.0 m


The mass of an object inside a space ship, traveling at 50% of the speed of light, is 2 kg; what mass would an observer on earth measure?

2.3 kg


Lower energy photons have...

Lower frequencies


One phenomenon or experiment that supports the wave theory of matter is...

The double-slit experiment with electrons


Which is not predictable in the double-slit experiment with electrons?

The individual impact point of each electron on the screen


A certain type of atom has only four energy levels as shown. The total number of spectral lines produced by this element is...



According to Heisenberg’s uncertainty principle, electrons are more unpredictable than a baseball. This is because electrons...

Have a smaller mass


An electron (m = 9.1 x 10-31 kg) has an uncertainty in its velocity of 0.5 m/s (Δv = 0.5 m/s). How large must its position be uncertaintybe? Give answer in millimeters. Remember: h = 6.6 x 10-34 J•s (1 J•s = 1J/Hz). Use (Δx)(Δv) ≈ h/m.

1.5 mm