LON-CAPA at McMaster Physics & Astronomy
Units · Metric prefixes · Constants


Useful links: Units, Metric prefixes, Physical constants

How to log into LON-CAPA

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.

How to enter answers

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.

Entering numbers

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 × 101. 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/s2 --> kg*m/s^2
To recap: use * for multiplying units, / for dividing units, and ^ for raising the unit to a power.

LON-CAPA for the most part will accept equivalent units, such as ft3 instead of m3. 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.