In PH1311 you will encounter numeric problems requiring calculation. These are not difficult and can be solved easily if you don't make any dopey mistakes. I'm going to show you a process that could help you avoid such boners.

Here's one we have seen in 1311:

The Moon's mean orbit radius is 385,000 km and its sidereal period is 27.322 days. Calculate the Moon's orbital velocity in km/hr.

If you grab your calculator and plow in here, you will commit the error characteristic of inability to analyze a problem and see into it. You'll end up dividing 385,000 by 27.322 to get km/day, then dividing again by 24 to get km/hr, yielding 587.133... km/hr. Neat, clean, quick and WRONG! This occurs multiple times each term.

Let me lay out a process for your use in these cases and see if you can find the error

1. Read the whole problem statement carefully. Visualize the problem. Maybe make a sketch of the layout. See how it works.
2. What parameters are given (stated in the problem)? You are given the radius of the Moon's orbit and the time for one orbital revolution.
3. What is the unknown you must find (calculate)? You must calculate how fast the Moon moves in its orbit. This must be in km/hr.
4. What formula(a)/equation(s) will you use for the solutions? You need km/hr, so you will divide a distance (km) by a time (27.322x24) hr. This will yield km/hr.
5. Do you have enough data given to solve the problem? Be careful here. Do you in fact have the values you need? Make a sketch of the Earth-Moon system and label it with the given values. Draw a circle around Earth and add labels. Draw a line from Earth to Moon and label it with the radius value given (385,ooo km). Label the orbit with the period (27.322 days). You need the distance the Moon travels in 27.322 days. Do you have it? Look closely. Can you see the error in the example above where the obvious calculation is wrong?
6. If you are not given the value you need to find the correct result, do you have enough data to get it? Going along here, you see that you do NOT have the actual value you need for solution but you have enough data to get it. The Moon does not travel back and forth along the radius of its orbit; it moves around the circumference of the orbit. You can see that in the sketch. Now can you see the error? You need the orbit circumference but you have the radius. No problem - the circumference is 2pi times the radius. You will divide 2pi times 385,000 by 27.322 times 24. You get 3689.07 km/hr.
7. Check your result. Look up the Moon's diameter - 3474.2 km. Divide that by its speed and get 0.9418 hrs. This is about 56.5 minutes, which is saying that the Moon moves its diameter in about 56.5 minutes, which is exactly what is observed.

Here's a another summary of the process. For each problem write out the following items.

1. Your understanding of the problem. What are you asked to find?
2. What formula/equation applies here? Write it down.
3. Your plan for solving the problem. What data do you need? What data are you given? Is there anything you need that is not given? If so, do you have enough data to get it?
4. Execute your plan and reach a solution.
5. Look at you r result(s) and do a sanity (reasonableness) check. Are the final units right (make sense in the situation)? Is the result reasonable (about what you would expect)?