# 20.181:hw11 sols

(Difference between revisions)
 Revision as of 19:03, 11 December 2006 (view source)← Previous diff Revision as of 19:12, 11 December 2006 (view source)Next diff → Line 22: Line 22: There is only one way to combine the given data so as to produce our desired units: There is only one way to combine the given data so as to produce our desired units: + + $\frac{1\times10^9}{M\cdot sec}\cdot \frac{1 \mbox{ } mole}{6.023\times10^{23}} \cdot \frac{1}{1 \times 10^{-15} \mbox{ } L} = 1.66 \mbox{ } sec^{-1}$ + + ----- + + Part 3:

## Revision as of 19:12, 11 December 2006

Solutions to HW 11

Part 1:

To complete the code shell provided, you had to insert something like the following code snippet:

           tau_new = (a_i_old[rxn] / (a_i_new[rxn]+eps)) * (tau_i[rxn] - t_cur) + t_cur
tau_i[rxn] = tau_new
a_i_old[rxn] = a_i_new[rxn]


note that you can't update a_i until after you've calculated a new tau.

Part 2:

An easy way to solve this question is with dimensional analysis. If you've never heard of dimensional analysis before, it's essentially a fancy way of saying: manipulate the data to produce a value with the correct units; more often than not, this value will also be the correct quantity.

For instance, we know that we're trying to calculate the probability per unit time that a particle collision causes a reaction. Our solution should therefore be in units of [1/time] (probabilities are unitless!).

There is only one way to combine the given data so as to produce our desired units:

$\frac{1\times10^9}{M\cdot sec}\cdot \frac{1 \mbox{ } mole}{6.023\times10^{23}} \cdot \frac{1}{1 \times 10^{-15} \mbox{ } L} = 1.66 \mbox{ } sec^{-1}$

Part 3: