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

 

  1. Know scientific notation and be able to recognize that 0.003 is the same as 3.0E-3.
  2. Know the characteristics of science and pseudoscience
  3. Know the SI units for some of the basic quantities we have been working with
    1. Position – m (meters)
    2. Time – s (seconds)
    3. Speed – m/s
    4. Acceleration – m/s^2
    5. Force – N (Newtons)
    6. Mass – kg (kilograms)
    7. Energy – J (joules)
    8. Power – W (watts)

 

II Scalars, Vectors, Tensors

 

  1. A scalar is a quantity that is just a number
  2. A vector quantity has a magnitude and direction: for example you might have a velocity of 70 mph East
  3. A tensor is a generalization of these quantities in multiple dimensions. The rank of a tensor gives the dimension.
    1. Rank 0 is a scalar
    2. Rank 1 is a vector
    3. 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.
  4. Know that vector quantities add. Be able to add vectors in a case such as a boat in the river.

 

III Motion

 

  1. Know the definition for
    1. Position
    2. Velocity
    3. Acceleration
  2. What is speed?
  3. Be able to look at a graph and determine position, velocity, acceleration
    1. Where are position, speed, acceleration the largest
    2. Where are they zero
  4. Be able to describe the for three special cases
    1. Motion in a line with no acceleration
    2. A ball twirled around on a string
    3. A ball thrown up in the air and falls back down

 

IV Special Relativity

 

  1. Two postulates of special relativity
    1. The speed of light is a constant independent of the speed of the source
    2. Physical laws are the same in all inertial reference frames
    3. An inertial reference frame is one that is not accelerating
  2. Moving clocks run slow. This is called time dilation.
  3. Know the equation to calculate how much longer a click takes in a moving clock given a speed in v/c.
  4. Moving objects appear shorter. Know the equation for length contraction.
  5. 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.
  6. Know what is meant by E=mc^2
  7. What are the fractions of mass converted for various reactions
    1. Matter-antimater 1
    2. Fusion – 0.007
    3. Fission – 0.001
    4. Chemical – 10-10
    5. Mecanical – 10-15
  8. The Sun uses fusion to convert matter to energy by fusion hydrogen to helium.
  9. 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

 

  1. Time is the thing measured by clocks
  2. Time is relative and depends on the speed of the observer, or how close the observer is to a mass
  3. General relativity says that time is a dimension in space-time

 

VI Force

 

  1. A force is a push or pull
  2. Force can be defined by Newton’s three laws
    1. If the sum of forces is zero, the object will not accelerate
    2. F=ma
    3. To have a force, there has to be an equal and opposite force
  3. Know the implications of Newton’s laws, e.g. that the Moon pulls as hard on the Earth as the Earth does on the Moon
  4. 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

 

  1. For over 6000 years people have tried to understand the motions of the planets and stars.
  2. Ptolemy developed an accurate Earth centered system in around 100AD that was accepted for 1400 years. This was based on deferents and epicycles.
  3. Tyco Brahe made detailed measurements that allowed Johannes Kepler to develop his three laws of planetary motion based on a Sun centered model.
  4. Newton unified all observations and laws in his Universal Law of Gravity

 

VII Gravity

 

  1. Know Newton’s law of gravity and be able to use it to calculate the force of gravity between two masses.
  2. Know why an astronaut in orbit is weightless
  3. Know that the Earth’s 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

 

  1. Einstein developed the theory of General Relativity
  2. The main postulate is that we can’t distinguish gravity from acceleration in the opposite direction
  3. Space and time are combined into a 4-dimensional space time
  4. Mass warps space-time. What we experience as gravity is actually curved space
  5. Time slows down near a large mass. This is called gravitational time dilation.
  6. Time travel may be possible, but this leads to paradoxes that need to be resolved.