Can you get better at solving physics problems

[James West]

I am taking an introductory physics course at college right now and honestly, I'd rather take an uppercut to the jaw then take another physics class. I'm great at Mathematics(that's my major) but I just can't seem to get any physics problems. I have so much trouble setting them up and solving them. Is there a strategy to solving these problems or is it just something that has to click?

 

[PeroK]

I am taking an introductory physics course at college right now and honestly, I'd rather take an uppercut to the jaw then take another physics class. I'm great at Mathematics(that's my major) but I just can't seem to get any physics problems. I have so much trouble setting them up and solving them. Is there a strategy to solving these problems or is it just something that has to click?

Can you give an example?

 

[gmax137]

practice practice practice...
I have been out of school for a long time, and I felt I had lost my touch. Someone here mentioned Irodov's book of problems, so I found that and started in. The first problems took me a long time, but I think I'm getting better at them.

 

[James West]

Can you give an example?

You build a 2.6-kg mound of mashed potatoes on a kitchen scale (which is a spring scale). You then use a large spoon to press on the top of the mound at a constant force of 3.8 N. While you are doing this, the scale reading increases by 5.0%. What is the acceleration of the center of mass of the potatoes while pushing with the spoon? Assume that vertically upward is the positive direction.

In this problem, I just couldn't set it up and I couldn't figure out why you have to use the increased weight on the scale for the acceleration when calculating force even though the acceleration is technically still the same. I now get that the scale is a normal force but its things like this that are constantly tripping me up and giving me grief.

 

[PeroK]

You build a 2.6-kg mound of mashed potatoes on a kitchen scale (which is a spring scale). You then use a large spoon to press on the top of the mound at a constant force of 3.8 N. While you are doing this, the scale reading increases by 5.0%. What is the acceleration of the center of mass of the potatoes while pushing with the spoon? Assume that vertically upward is the positive direction.

In this problem, I just couldn't set it up and I couldn't figure out why you have to use the increased weight on the scale for the acceleration when calculating force even though the acceleration is technically still the same. I now get that the scale is a normal force but its things like this that are constantly tripping me up and giving me grief.

It may not be much help, but I have no patience with questions like that. There are no many things wrong with it. Not least that, IMO, it makes a mockery of physics and divorces it from having any practical value.

But, I guess your issue is to separate the physics from the nonsense. Maybe parse out the rubbish? I might do something like:

2.6 kg mass ... downward force of 3.8N ... increased scale reading of 5%. What is the acceleration of the centre of mass? (Don't forget gravity.)

 

[Rive]

Is there a strategy to solving these problems or is it just something that has to click?

There is no way to spare the work: you have to practice a lot.
To console you, I have to mention that these kind of problems (your example) are not really about physics: they are about linking the real world and physics equations/tools/descriptions together, so later on you could translate from 'real' to math. This also means they have an unique language, full with (dumb) tricks and occasionally: hints.
Give 'em a chew, it'll kick in.

 

[nuuskur]

I am a math major, too and as such I would say look up relevant definitions or formulas. Performing the calculations should be a trivial task.

 

[gleem]

Mathematicians do not necessarily have an advantage solving physics problems.

Physics is all about understanding the meaning of the data and identifying the appropriate relationships in the data. Sometimes you have to determine or tease out what lies beneath the given information

 

[robphy]

What helped me in being a better problem solver is writing detailed solutions to problems from first principles,
explaining steps along the way [to a reader, e.g. my future self reviewing these problems].
After a while, you can see the pattern and develop some strategies.
(The method is more important than just the answers.)

 

[vela]

Is there a strategy to solving these problems or is it just something that has to click?

Have you checked your textbook? Modern textbooks do focus on how to solve problems in addition to the physics itself because a lot of students (like you) struggle with problem solving.

 

[nineteen]

Let me start out like this. I am a Advanced Level student in Sri Lanka. We too have a very competitive examination when it comes to the final examination. However, to overcome all these lapses in calculations, understanding and all that stuff, what we are doing is we are practicing a hell of a lot of times.

We do the same problems we solved at school, after we come back home. Same stuff, but we practice the method until a mold for those type of questions is made in out brains. We don't solve all the problems we did at school everyday, but we atleast do so with the hard and difficult problems. I myself practice each difficult question about 14 times.

The key for getting better at solving problems is understanding. Not mathematics or whatever. You should have the experience in all those stuff. When you have leisure just observe all the physical happening and try to understand them. Try to imagine all the stuff they say in a particular problem. When it comes to physics imagining stuff plays a key role in solving problems.

Solving problems is also like a sport, it is also like mastering a certain musical instrument. Practice, practice and practice, after that start practicing again.

 

[Dr. Courtney]

https://www.youtube.com/user/BearTrueFaith/videos?sort=da&view=0&flow=grid
The above link demonstrates a number of careful solutions. The thing you most likely need to learn is a standard problem solving approach, and all the above examples use one called the IDEA problem solving format. IDEA stands for:

Interpret - draw a picture, make sure you understand the physical and geometrical information in the problem, what you are given and what you are asked to find. All these aspects should be represented in your picture or diagram.

Develop - make a plan to solve the problem. Identify (and write down) the overriding principle of physics (for example Newton's second law or Conservation of Energy) needed to solve the problem. Identify (and write down) a likely series of steps. Some steps one uses a lot are convert all units to SI, compute x and y components of all vectors, solve for some quantity as an intermediate result en route to your final answer. (For example, computing the flight time is often a helpful intermediate step in projectile motion problems.)

Evaluate - This is the first step where you'll be writing down equations. Prematurely writing down equations is the dangerous game of formula roulette, because you're guessing at formulas without an intentional process. Here, you execute the plan you developed in the earlier step.

Assess - Does your answer make sense? Are the sign, units, and magnitude sensible? Did you answer all the parts of the question you were asked? Did you double check your work?

 

[Dr. Courtney]

This video explains nicely:

 

[gleem]

The above link demonstrates a number of careful solutions. The thing you most likely need to learn is a standard problem solving approach, and all the above examples use one called the IDEA problem solving format. IDEA stands for:

This seems to have been adapted from George Polya's http://web.mnstate.edu/peil/M110/Worksheet/PolyaProblemSolve.pdf

• Understand the problem
• Devise a plan
• Execute the plan
• Look Back