Units · Metric prefixes · Constants

Useful links: Units, Metric prefixes, Physical constants

Once your name appears in Avenue to Learn for a course using *LON-CAPA*, an account will
be set up for you on the McMaster Physics
and Astronomy *LON-CAPA* server.
Log in at
loncapa.mcmaster.ca.
Your username will be your macid, and **your initial password will be your student
number.**
On your first visit, change your password:

**select Main Menu at the top left, then Set User Preferences, and click on Password.**

Your password is stored as an encrypted hash, and we cannot recover it if you forget it.
A button on the login page allows you to have your password reset, using your
**McMaster e-mail account** ("macid@mcmaster.ca").

If you register in the course after the beginning of term during Drop and Add, it
will normally take a day for you to appear in Avenue to Learn, and another working day before you
appear in *LON-CAPA*. If your student number begins with zero,
your initial password *may* not have the have the leading zero
(*e.g.,* if your student number is 0123456, try both 0123456 and 123456 as an initial password).
If you are still unable to log in, or unable to reset your password,
contact the *LON-CAPA* administrators using the **Contact Helpdesk** link on the
*LON-CAPA* login page; or
if necessary, e-mail
them at
loncapa@physics.mcmaster.ca.
Be sure to include your name, student number, macid, and course.

After each part of each problem, there is a box for the answer, followed
by a button labelled **Submit Answer**. Once you have entered your
answer, click the button. *LON-CAPA* will then check your answer.

Note: you can enter answers for several problems, then click the
**Submit All** button at the bottom to submit all of the entered answers.
However, it's probably easier to do one at a time. It isn't
necessary to answer all of the problems in one session; you can answer a
few, exit *LON-CAPA*, and log back in later to finish.

*LON-CAPA* checks for the correct
units first. It is smart enough to know, for
example, that "km/h" and "m/s" are both units of speed,
and will accept answers in either unit. You can use any of the standard
metric prefixes. For example,
100 cm and 1 m are the same.

Next, *LON-CAPA* checks for significant figures. The
number of sig figs necessary should be determinable from the numbers used
in the problem. Sometimes a range of the number of sig figs will be allowed
(e.g., 12.3, 12.34, and 12.345 may be acceptable, but 12 and 12.3456 may
not be). Usually 2 or 3 significant figures are required.

Note: if you get the units wrong, or significant figures wrong, no tries are
deducted from the number of tries remaining. Also, if
*LON-CAPA* tells you that your units or sig figs are wrong, it
does not mean that your numerical answer is right!

Finally, *LON-CAPA* checks whether the answer is
correct. If it isn't, a try is deducted. You will have (usually) at most 10
tries available. If it is correct, *LON-CAPA* will say
so, and remove the **Answer** box.

There are two ways to enter numbers, which are best described by an example.
Say you have `21.3`. This can be entered as either `21.3`, or in
scientific notation as `2.13e1` (or `2.13E1`). The latter is
equivalent to 2.13 × 10^{1}. Don't use spaces with scientific
notation: `2.13E1`, **not** `2.13 E 1`. Also, don't
use commas: `213000`, not `213,000` or
`213 000`. An ambiguous number such as `120` is treated as
two significant figures, while `120.` and `1.20e2` have three sig figs.

See the units page for a list of the units that CAPA
accepts. It accepts most SI units, and some Imperial ones too. Units can
be prefixed by one of the metric prefixes, so if
the answer to a question is 1000 g,
then 1 kg is considered to be equivalent. There **must be a space**
between the number and the unit.

Compound units should be written using *, /, and ^, so that

kN·m | --> | kN*m |

J/m | --> | J/m |

kg·m/s^{2} |
--> | kg*m/s^2 |

*LON-CAPA* for the most part will accept equivalent
units, such as ft^{3} instead of m^{3}.
However, it may sometimes get confused with
more complex expansions, such as N/C which is the
same as V/m. In this case, try different
combinations.