athena21

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Hey guys, I just took AAMC VI and did well on physical sciences--unfortunately by guessing...so here are a few questions I could use help with...

The ionization constant, to a first approximation, of H(2)S is:
A) Near zero
B) Much less than 1
C) about 1
D) much more than 1

The motion for small displacements x is characterized by two dimensional constants, K and M. Identify by dimensional argument the correct formula from which the period T can be calculated. maximal displacements x = -A and A
A) (T/pi)square = 4K/M
B) (T/pi)square = 4K*M
C) (T/pi)square = 4M/K
D) (T/pi)square = 4/(K*M)

The spring constant K can be computed from the internal energy E and the amplitude A by:
A) K = A squared * E
B) K = A * E
C) K = E/A
D) K = E/A squared

How many grams of lead(II) Iodide are present in 100ml of a saturated aqueous solution? (Solubility S = 1.89 x 10(-3))
A) .0410 g
B) .0871 g
C) 2.470 g
D) 8.71 g

In a healthy person standing at rest, a comparison of arterial blood pressure measured in the arm with taht measured in the leg shows that the pressure is :
A) lower, because the blood flow rate is less
B) lower, because the viscous flow resisitance causes pressure loss
C) the same, because viscous pressure loss precisely compensates the hydrostatic pressure increase
D) greater, because the column of blood betwen the arm and the leg has a hydrostatic pressure

any help is appreciated! thanks!
 

WingMD

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1) Because H2S is a weak acid, the Ka will be small and because most weak acids have a Ka less than 1, then its ionization constant will be much less than 1.

2) Look at the units. T^2 = s^2. So according to the equation given F=Kx or F=Kx=Ma=M(m/s^2) Do a little rearranging and you will get Mm/Kx = s^2.

3) The equation is given PE=Kx^2/2. Again, rearrange the equation such that you get K = 2PE/x^2

4) The Molar concentration is given in the passage for PbI which is 4.6x10^-6 moles/L. You are given the volume of PbI, so just cancel out the units by multiplying with the molecular weight and you should get the grams of the PbI.

5) Pressure is always greater with depth. The equation
P = Density x depth x gravity. Because the leg is lower than the arm, then you should get a greater pressure.
 

freakazoid

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Quick note on 3: Don't forget that the effective spring constant is 2K . . . .
 
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A

athena21

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sorry, stupid question...but why is the effective spring constant 2K if they are in opposite directions? they're not really helping each other out...i guess constants don't have direction...i dunno...
 

freakazoid

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This might not matter anymore, but the idea is a spring force always provides a restoring force, no matter which way it is being pulled. Imagine, if you push it one way, the compressed spring wants it to go the other way, and the elongated spring wants it to go the SAME way. Both of them act to "restore" the particle to its resting position.