Now we come to less trivial situations involving Newton's Laws.
A lot of these problems can seem darned near impossible if you
don't go about solving them the right way. It takes a lot of
self-discipline to logically apply Newton's laws to obtain the
correct answer. Remember this is physics, not philosophy. The
answers you get can be tested experimentally. *There are never
two right answers to well posed physics problems*. So if you
get stuck **do not:**

- Write down something that you know is wrong and continue.
- Decide to guess an equation.
- Decide to guess an answer.
- Fudge your solution because you think you know the answer right answer and it's just not working out the way you think.

Instead, realize that the answers are derivable from Newton's laws. You just need to be logical enough to see how to do it. In order to aid you, you should follow the following advice. If you don't, you have nobody but yourself to blame when you screw up.

- Draw a diagram. If you want, draw a rough sketch to get yourself off the ground. Then identify all the forces in the problem. You saw an example of this above with the picture of the hand and the weight in fig. 1.4.
- Draw a ``free body diagram'' for each object. That is, draw a picture of an object, and draw only those forces that act on the object. Include all the forces that act on the object.
- Figure out a good coordinate system to use for each object. That
is how the coordinate system is to be oriented. Them apply
in component form. That is for the x and the y components separately.
**Remember to use symbols such as etc. instead of numbers like***3 kg*. - Solve the equations. If you've done everything right, you should be able to solve for all your unknowns.
- Check limiting cases. What happens if this mass goes to zero?
This one to infinity. What if this angle becomes 90 degrees? You
get the idea. If all the limiting cases seem to make sense, and the
units check out, then you've probably solved the problem correctly.
If they don't check out, at least now you'll have a clear logical
description of your work and will be able to go over it to check for
mistakes.

Now let's looks at some examples.

Wed Jan 7 17:12:17 PST 1998