PHY 240 FINAL REVIEW

2-D Velocity Transforms: So I’m sitting in
my space station minding my own business with my
alien friend, Yalgrae when all of a sudden the alarm goes
off! We are being attacked by the evil Druqon! We hop
in our space pods and leave the station. I travel in (what
I am calling) a positive x-direction at 0.825c, whereas
Yalgrae leaves in the direction shown at 0.750c. As I
look back, (a) what is the x-component of Yalgrae’s
velocity that I observe? (b) What is the y-component of
Yalgrae’s velocity as observed by me, and (c) in what
direction do I see Yalgrae’s moving? (d) In what direction
does Yalgrae see me moving?

Work and Energy: (a) What is the electric
potential at the origin in the picture shown? (b) Determine the
work done in moving a charge, q4= +5.0e from infinitely far
away to the origin in the picture shown. (in eV and J)

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Find the momentum, kinetic energy, and total energy of a Pfeileon (rest mass=425
MeV/c2) moving at a speed of 0.742c

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NGSS.HS-PS2-2

NGSS.HS-PS3-2

Relativistic Energy: The figure to the right shows the relativity
mnemonic triangle for six particles; the hypotenuses 2 and 4 have the same
length. Rank the particles according to (a) rest mass, (b) momentum
magnitude, and (c) Lorentz factor, γ, greatest first. (d) Identify which two
particles have the same total energy. (e) Rank the three lowest-mass particles
according to kinetic energy, greatest first.

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What is an “inertial” reference frame? Is this classroom an inertial reference frame?

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Our Good Friend Al: Please state, or explain, Einstein’s two fundamental
postulates of special relativity.

What is the “correspondence principle” Does it hold for the special relativity we have
been working with in class?

A rod is to move at constant speed v along the x axis of reference frame S, with the rod's
length parallel to that axis. An observer in frame S is to measure the
length L of the rod. Which of the curves in the figure to the right best
gives length L (vertical axis of the graph) versus speed parameter β?

Electron Waves: If you recall the Davisson-Germer experiment, electrons are
scattered off of a Ni crystal (d=0.215 nm) and exhibit constructive interference at some
particular scattering angles, depending on their wavelength (n(wavelength) = d sin theta) is the scattering
equation). Suppose we accelerate electrons through a 175.0 V potential difference. (a) What
is the kinetic energy of these electrons? (b) What is the momentum of these electrons? (c)
What is the deBroglie wavelength of these electrons? (d) At what angle(s) will scattered
electrons be detected? (Note that, with a 200 V accelerating potential, these are definitely
NOT relativistic electrons!) (Use eV and nm and c units throughout this entire problem... NOT
J and m and m/s.

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NGSS.HS-PS4-1

Thank You Al!: UV light with frequencies ranging from
about 8.00 x 1014 Hz to about 3.00 x 1016 Hz is incident on a polished
piece of metal. Some frequencies of light succeed in ejecting electrons
from the surface of the metal. The maximum KE with which electrons are
observed being ejected from the metal is 117.7 eV. (1.00 eV = 1.60 x
10 -19 J) (Pay close attention to units in this problem!!)

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