Exam #1 Study Guide:
Exam 1 will have 40 multiple choice question based on
material covered in lectures up to 9-22. The exam will not cover any material
on electricity or magnetism. That will be covered on exam number 2.
A few of the questions will involve simple calculations, so
you should bring your calculator. You will not need your clicker.
You may bring one double sided sheet of paper with notes to
the exam.
I Basics
- Know
scientific notation and be able to recognize that 0.003 is the same as
3.0E-3.
- Know
the characteristics of science and pseudoscience
- Know
the SI units for some of the basic quantities we have been working with
- Position
m (meters)
- Time
s (seconds)
- Speed
m/s
- Acceleration
m/s^2
- Force
N (Newtons)
- Mass
kg (kilograms)
- Energy
J (joules)
- Power
W (watts)
II Scalars, Vectors, Tensors
- A
scalar is a quantity that is just a number
- A
vector quantity has a magnitude and direction: for example you might have
a velocity of 70 mph East
- A
tensor is a generalization of these quantities in multiple dimensions. The
rank of a tensor gives the dimension.
- Rank
0 is a scalar
- Rank
1 is a vector
- Rank
2, or higher, describes a more complex quantity that has two directions
and two magnitudes. The metric of space-time, or
the curvature of space time are examples.
- Know
that vector quantities add. Be able to add vectors in a case such as a
boat in the river.
III Motion
- Know
the definition for
- Position
- Velocity
- Acceleration
- What
is speed?
- Be
able to look at a graph and determine position, velocity, acceleration
- Where
are position, speed, acceleration the largest
- Where
are they zero
- Be
able to describe the for three special cases
- Motion
in a line with no acceleration
- A
ball twirled around on a string
- A
ball thrown up in the air and falls back down
IV Special Relativity
- Two
postulates of special relativity
- The
speed of light is a constant independent of the speed of the source
- Physical
laws are the same in all inertial reference frames
- An
inertial reference frame is one that is not accelerating
- Moving
clocks run slow. This is called time dilation.
- Know
the equation to calculate how much longer a click takes in a moving clock
given a speed in v/c.
- Moving
objects appear shorter. Know the equation for length contraction.
- Time
dilation has been proven by comparing clocks at the North Pole and
equator, by clocks flown in airplanes, and by the lifetimes of subatomic
particles.
- Know
what is meant by E=mc^2
- What
are the fractions of mass converted for various reactions
- Matter-antimater 1
- Fusion
0.007
- Fission
0.001
- Chemical
10-10
- Mecanical 10-15
- The
Sun uses fusion to convert matter to energy by fusion hydrogen to helium.
- The
Sun can burn for 10 billion years. The Earth is about 5 billion years
old, so the Sun should last for another 5 billion years.
V What is time
- Time
is the thing measured by clocks
- Time
is relative and depends on the speed of the observer, or how close the
observer is to a mass
- General
relativity says that time is a dimension in space-time
VI Force
- A
force is a push or pull
- Force
can be defined by Newtons
three laws
- If
the sum of forces is zero, the object will not accelerate
- F=ma
- To
have a force, there has to be an equal and opposite force
- Know
the implications of Newtons
laws, e.g. that the Moon pulls as hard on the Earth as the Earth does on
the Moon
- Be
able to calculate a simple F=ma problem. For a given force, if we double
the mass, what happens to the acceleration?
VII History of Astronomy
- For
over 6000 years people have tried to understand the motions of the planets
and stars.
- Ptolemy
developed an accurate Earth centered system in around 100AD that was
accepted for 1400 years. This was based on deferents and epicycles.
- Tyco Brahe made detailed measurements that allowed Johannes
Kepler to develop his three laws of planetary
motion based on a Sun centered model.
- Newton
unified all observations and laws in his Universal Law of Gravity
VII Gravity
- Know Newtons
law of gravity and be able to use it to calculate the force of gravity
between two masses.
- Know
why an astronaut in orbit is weightless
- Know
that the Earths gravity extends to astronauts in orbit. Know that the
magnitude is about the same as it is on the surface of the Earth.
VII General Relativity
- Einstein
developed the theory of General Relativity
- The
main postulate is that we cant distinguish gravity from acceleration in
the opposite direction
- Space
and time are combined into a 4-dimensional space time
- Mass
warps space-time. What we experience as gravity is actually curved space
- Time
slows down near a large mass. This is called gravitational time dilation.
- Time
travel may be possible, but this leads to paradoxes that need to be
resolved.