10 th grade science Must DO In your notebook write a reflection on the assembly yesterday What did you appreciatenot appreciate What inspireddiscouraged you How do you feel about the quest to achieve the IB diploma ID: 512128
Download Presentation The PPT/PDF document "The principle of special relativity" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
The principle of special relativity
10
th
grade scienceSlide2
Must DO!
In your notebook, write a reflection on the assembly yesterday.
What did you appreciate/not appreciate?
What inspired/discouraged you?
How do you feel about the quest to achieve the IB diploma?Slide3
In the nineteenth century Physics was solved!
Scientists had a complete understanding of nature
Mechanics had been triumphed!Slide4
In the nineteenth century Physics was solved!
Scientists had a complete understanding of nature
Mechanics had been triumphed!
Applications to engineering!
Slide5
In the nineteenth century Physics was solved!
Scientists had a complete understanding of nature
Mechanics had been triumphed!
Applications to engineering
!
Kepler
solved the motion of the planetsSlide6
In the nineteenth century Physics was solved!
Scientists had a complete understanding of nature
Maxwell showed that electricity and magnetism were the same thing (electromagnetism)
Hey
Gurl
…Slide7
In the nineteenth century Physics was solved!
Scientists had a complete understanding of nature
The kinetic theory of gasses gave us an understanding of matter at a molecular level.
Slide8
HOWEVER!! (duhn
Duhn
Duuhhaaaaa
)Two problems defied solution and were threatening to bring down the entire structure of classic mechanics.
1) Physicists were trying to understand the spectrum of “black body radiation.”
Which has been resolved and involved photons and quantum mechanics.Slide9
HOWEVER!! (duhn
Duhn
Duuhhaaaaa
)Two problems defied solution and were threatening to bring down the entire structure of classic mechanics.
2) The second problem had to do with the speed of light.Slide10
Young Einstein Was said to have pondered
…Slide11
Young Einstein Was said to have pondered
…Slide12
This puzzle was sovled
by
…
Albert Einstein’s “Special Relativity!”Slide13
Create a new unit in your science notebook
Special and General Relativity
Create a Unit cover page
Create a new WWK page
Create a new “Must do’ page
Title the next right blank page “Frames of Reference” Slide14
Objectives (write these down)
State the meaning of the term
frame of reference;
State what Galilean relativity means;
Solve problems of Galilean relativity;
Understand the significance of the speed of light;
State two postulates of the principle of relativity
;
Appreciate that absolute time does not exist and that simultaneity is a relative concept.Slide15
WWK
Frame of reference – The observer along with the rulers and clocks that he or she uses to measure distances and times.
Inertial frame of reference – Frames moving with uniform velocity past each other on straight lines. (When the observer is not accelerated (does not speed up, slow down, or change directions.))Slide16
Example of single frame of reference
In this frame of reference the observer decides that lightning struck at time t = 3 s at position x = 60 mSlide17
You do!
Use the internets to find an example of a relative frame of reference.
Hint: this example must include two frames of reference.Slide18
Relative Frame of reference example
Consider two observers, one on the ground within sight of a moving train and another in the train. The train moves past the observer on the ground at t = 0s going v = 15 m/s and is struck by lightning three seconds later. Draw a diagram of this scenario
Hint: a diagram is not a sketch. A diagram has all important information and, in this case, shows the passage of time. Slide19
Relative Frame of reference example
With a partner, convert the equation x’ = x –
vt
into a sentence contextualizing the train problem.Slide20
Newton said…
“Absolute, true and mathematical time, of itself, and from its own nature, flows equably without any relation to anything external.”Slide21
The equations…
x
’ = x –
vt
t
’ = t
…
reflect a Galilean transformation: the relation between coordinates of events when one frame moves past the other with uniform velocity on a straight line. (aka: inertial frames of reference.)
It is impossible for one of the observers to claim that he or she is ‘really’ at rest and that the other is ‘really moving’ when there is no acceleration.Slide22
Video review!Slide23
Galilean Relativity and the law of addition of velocities
Again, imagine the train with the two observers. Consider a ball rolling on the floor of that train with velocity u’ with respect to the observer on the train. Assume t’ = t = 0 s is the point when the ball stars rolling. After time t’ the position can be found at x’ =
u’t
’ by the train observer.
The ground observer records the position of the ball to be at x = x’ +
vt
(remember t’ = t)
Substitute in the equation x’ =
u’t
’ and you get x = (u’ +v)tSlide24
Galilean Relativity and the law of addition of velocitiesSlide25
Homework!
A ball rolls on the floor of the train at 2 m/s (with respect to the floor). The train moves with respect to the
gound
…
a) to the right at 12 m/s, b) to the left at 12 m/sWh
at is the velocity of the ball relative to the ground?
If we replace the ball with a beam of light moving with velocity c = 3 x 10
8
m/s, the formula from the example implies that light would be traveling at a higher speed relative to the ground observer.
Many experiments have been done to detect variations in the speed of light but none have ever been found!Slide26
Einstein’s PRinciple
of Special Relativity
Please title the next right blank page in your notebook “Special Relativity.”Slide27
The Speed of light
Remember
Maxwel
? (1864)
By unifying magnetism and electricity he also discovered the electromagnetic nature of light.
c
= 1/√(ε
0
μ
0
)
ε0
= electric permittivity
μ
0
= magnetic permeability
In other words the speed of light doesn't have anything to do with the speed of the object creating the light.
Hey
Gurl
…Slide28
The Speed of light
Einstein (1905) resolved the contradiction between
M
axwell’s findings and Galilean relativity.
Light doesn't need a medium to travel through The speed of light is the same for all observers
The laws of physics are the same in all inertial frames of reference.
Einstein modified Galilean transformation laws to reflect this. He also had to change Newtonian mechanics to relativistic mechanics.Slide29
From…Slide30
The principle of relativity
Remember: with inertial frames of reference it is impossible to scientifically prove which observer is moving and which is at rest. Further, both observers would arrive at the same laws of physics if they did the same experiments (Newton’s laws, v=x/t,
etc
)
This leads to the two principles of relativity:
The laws of physics are the same in all inertial frames.
The speed of light in a vacuum is the same for all inertial observers.Slide31
Implications
The speed of light in a vacuum is the same for all inertial observers
.
This means that time is not absolute!
“Absolute, true and mathematical time, of itself, and from its own nature, flows equably without any relation to anything external.”Slide32
Implications of relativity - spacetime
If the speed of a beam is the same for both observers they must measure different times of travel. Thus observers in motion relative to each other measure time differently.
SPACE AND TIME ARE INEVITABLY LINKED AND ARE NOT INDEPENDENT OF EACH OTHER!
Space and Time are now
SpacetimeSlide33
Implications of relativity – simultaneous events
With a partner read and discuss the hand out and answer the final question in your notebooks.Slide34
Implications of relativity – simultaneous events
Events that are simultaneous for one observer and which take place at different points in space, are not simultaneous for another observer in motion relative to the first.
On the other hand, if two events are simultaneous foe one observer and take place at the same point in space, they are simultaneous for all other observers as well.
SPACE AND TIME ARE INEVITABLY LINKED AND ARE NOT INDEPENDENT OF EACH OTHER!Slide35
Example question
Observer T is in the middle of a train carriage that is moving with constant speed to the right with respect to the train station. Two light signals are emitted at the same time as far as the observer, T, in the train is concerned.
Are the emissions simultaneous for observer G on the ground?
The signals arrive at T at the same time as far as T is concerned. Do they arrive at T at the same time as far as G is concerned? According to G, which signal is first?