# Homework Help: General Approach to a Problem

1. Jul 14, 2009

### coco87

Hey,
I'm in my Physics 1 course now, and am having issues. I've done well in math, and will be entering Calculus 3 next semester. I usually have no issues doing calculations at all. The problem I seem to be having is with physics problems in general. Sometimes I have to derive a totally new equation from various other equations, many times I don't believe I'm giving enough data (however, jumping through hoops, I can usually derive more data from the data I already have), and many times I just read a problem and draw a blank. I have a feeling I might not be too good at approaching "word problems". I love physics, especially attempting to solve the problems; but find myself looking at solutions to either point me in the right direction, or to figure out where I should go from various points in a problem. This is obviously not a very good strategy (considering I won't be-able to find a solution or help for some problems). Would anyone have any tips, ideas, anything that would help me with an overall approach to a problem in general? Pretty much how to approach a physics problem. I apologize if this is too vague, but I'm not quite sure how else to describe it.

Thanks for any help

2. Jul 14, 2009

### Staff: Mentor

I'm surprised to see that you have difficulty with word problems, having gotten through two calculus courses. Many of the problems in integral calculus are physics problems (particularly work, pressure, and the like) that are typically presented with text descriptions. E.g., find the total work required to pump water from a tank of a certain shape to a point 5 feet above the top of the tank. For a problem like this you need to take the given information and find a typical volume element of water, calculate its weight, and determine how much work is required to lift (pump) it to the given point. After you have done that, you're pretty much ready to set up your integral.

Also, the related rates problems you saw in your first calculus course are almost always presented as word problems, and what you have to do is translate the information given in the problem into equations that you can differentiate to get the rates (derivatives) for the quantities.

Probably the best advice I can give to help you improve with the physics problems is to look at the worked examples in your text, and make sure you understand every step, and to do a bunch of the problems in your text. Pick ones whose answers are given to compare your answer with that in the back of the book. The more practice you have at this, the better you'll get. For the ones you can't figure out, post them here. There are lots of people who are willing to help you out.

3. Jul 14, 2009

### cepheid

Staff Emeritus
Dealing with a physics word problem is reading comprehension as much as it is physics. I would say that a first very important step is to extract from the problem all of the given/known physical quantities and list them. That way you have it right in front of you exactly what information has been provided. This technique is particularly useful to the style of problems given in introductory physics. As the previous poster has pointed out, one would expect some of this to be old hat to you by now.

Next you want to identify what key physical principles or concepts are being tested. These principles are usually encompassed by certain equations that are applicable to the situation at hand. Notice however, that I didn't say to merely "choose" equations to used. I said to identify the physical concept. I think that it is very important to understand what idea the problem is testing, and not merely to blindly apply equations that seem related.

Our template for posting questions about homework problems on this forum summarizes a good approach to solving a problem quite nicely:

4. Jul 14, 2009

### coco87

Mark44:
In class we never really had many (if any) word problems on tests. Maybe some in homework, but I'd usually have to look at a solution to get an idea of how to solve it. I can't remember a-lot of the related rates part of calc 1, we might not have covered it that well. I agree with your practice makes perfect principle, that's what I usually do, but that takes a-lot of work (hard to find time to do it all), I try to do as many as possible.

cepheid:
I do believe you have a point there. I probably have an issue with comprehending the problems. I must say that I can't remember any of my college professors really focusing on word problems that much. One of my issues does seem to be blindly applying equations. Your steps for examining a problem appear to make sense, so I'll give them a shot.

Thank you both