Physics

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Author:
emmayarewhy
ID:
161541
Filename:
Physics
Updated:
2012-07-15 17:56:14
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phys mcat
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Momentum
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  1. When is momentum not conserved?
    If there are external forces acting along direction of velocity.
  2. If a monster truck hits a elephant and comes almost immediately to a full stop, what can you assume?
    That the monster truck applied a force to the log equal in magnitude to the force appplied by the elepphant to the monster truck
  3. If a girl on a sled are stationary and then the girl wants to walk backwards, what would happen?
    The girl would walk backwards slower than she would on dry ground, because sled would be opposing her motion to keep momentum zero. However, since the sled is heavier, it's happening at a slower rate than the girl is walking. This means that the girl will walk backwards at a slower rate than she would on dry land.
  4. If a girl is sitting in a sled and she wants to go north, what should she do?
    Throw something in the opposite direction you'd like to go, because after you throw something, the total momentum must be zero.
  5. Which is more damaging in a head on collision? An elastic or inelastic collision? Why?
    Inelastic collision. Even though elastic collision exerts a larger average force, there is no damage done to the identical colliding objects, because there is NO LOSS IN KINETIC ENERGY.
  6. When can momentum be conserved in the presence of friction?
    When you extend what you mean by internal forces - if you include air and ground into your system, then friction can be included as an internal force, meaning that momentum can be conserved.
  7. Can center of mass be where a mass is?
    NO! But can be underneath the mass if that's the best place.
  8. What is Newton's Second Law?
    F=ma
  9. What happens to the current when you have resistors in parallel and you remove one of the resistors?
    The total current in the circuit will decrease.

    This is because there's a constant voltage and removing a resistor in parallel INCREASES resistance. V=IR.
  10. If heat is supplied to a gas in a rigid container, how much work does the gas do after ten minutes? why?
    none. because there must be displacement for there to be work!
  11. In what scenario would a gas be doing negative work?
    If it was being compressed.
  12. At what point on titration curve would [H2PO4]=PO4 2-
    At the second half equivalence point.
  13. What is the normality of 24 g of 98 g H3PO4 in 1 L of solution?
    Answer: N= 0.75.

    Number of equivalent Hs x Molarity = Normality!!
  14. If a mass of 0.23 causes a spring to extend by 5 cm, what would a mass of 0.54 extend the spring by?
    Use ratios! 0.23/0.54=5 cm/x!
  15. How does the work done by an automatic pitcher change if you increase the angle to the horizontal of the barrel?

    Why?
    It will not change, because the air pressure behind the ball is the same.

    Because even if you increase angle, the angle between force and displacement stays zero.
  16. Which expression gives a consistent definition of an electron's "wavelength" if it has total energy E?
    Wavelength = hv/E
  17. In a medium, what formula gives the speed of light?
    v=c/n. In a vacuum, the speed of light = c.
  18. What happens to the environment when you inject a noble gas into the system?

    What happens to the pressure? The partial pressures?
    The only thing that happens is an increase in total pressure, but this doesn't affect the partial pressures of the other reagent gases.
  19. If you're asked to find a formula and there's a data table, what should you do?
    Plug numbers from the data table into your formula to see if its right.
  20. If light is going from a medium of higher n to a medium of lower n, how will the light refract?
    It will be refracted AWAY FROM THE NORMAL
  21. If light is going from a medium of lower n to a medium of higher n, how will the light refract?
    It will refract at an angle CLOSER TO THE NORMAL
  22. if pH < pKa, which is bigger? [H+] or Ka?
    [H+]

    This is because -log[H+]   <    - log Ka. Then, if you multiply them both by one, the inequality sign reverses:

    log [H+] > log Ka --> [H+] > Ka
  23. if pH > pKa...
    [H+] < Ka
  24. What types of acids yield the greatest conjugate base concentration?
    strong acids, because they dissociate more.
  25. What happens to pOH when pH increases?
    pOH decreases.
  26. What is the pH of salt water?
    7.0
  27. Which of the following rxns is NOT catalyzed by acid?

    Hydrolysis of:
    A. Disaccharides
    B. Esters
    C. Alkanes
    D. Popypeptides
    C. Alkanes, because everyone else can be broken down by acid.
    (this multiple choice question has been scrambled)
  28. How to determine energy emitted from ionization energies of each energy shell?
    Higher ionization energy - lower ionization energy
  29. How is the probability of an X-ray emission event at a given wavelength measured?
    By its intensity in the spectrum
  30. If 2 identical photoelectric devices are connected to the same electrical circuit, and the devices are connected in parallel with each other. Compared to the voltage generated by a single device, the total voltage supplied to the circuit by the parallel device will be:

    What if in series?

    A. 4x as large
    B. 2x as large
    C. 1/2 as large
    D. The same
    D. The same.

    This is because two identical voltage sources connected in parallel will produce the same as one voltage source.

    If it was two identical voltage sources connected in series, the total voltage supplied by the series devices would be 2x as much.
    (this multiple choice question has been scrambled)
  31. For a photon of energy hf to eject an electron from a material with a work function of phi, the photon's energy must be what in comparison to phi?
    It must just be larger than phi.
  32. What happens if you apply an additional absorption coating to a material, so that the conversion efficiency of E of Material A will be independent of wavelength
    E vs. wavelength will have a constant slope.

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