Solving difficult physics problems on exams.

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Discussion Overview

The discussion revolves around strategies for effectively tackling difficult physics problems on exams, particularly under time constraints. Participants share their experiences and approaches to problem-solving in the context of an introductory physics course.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant expresses concern about time management during exams and questions the effectiveness of drawing diagrams and listing knowns and unknowns when pressed for time.
  • Another participant emphasizes the importance of practice and suggests starting with simple diagrams, even if they are just boxes with force vectors, to aid understanding.
  • Some participants argue that relying on a "plug-n-chug" method may not lead to a deep understanding of physics and could be ineffective for complex exam questions.
  • There is a suggestion that with enough practice, students can develop an intuition for problems, making the process feel more like "plugging and chugging" as they become familiar with the necessary diagrams and variables.
  • One participant questions the necessity of drawing diagrams if they can arrive at the correct answer through simpler methods, highlighting a tension between thoroughness and efficiency.
  • Another participant reflects on the challenges of managing time when faced with multiple complex problems, suggesting that shortcuts might be beneficial in such scenarios.

Areas of Agreement / Disagreement

Participants express differing views on the balance between thorough problem-solving techniques and the need for efficiency under exam conditions. There is no consensus on the best approach, with some advocating for detailed analysis and others supporting a more streamlined method.

Contextual Notes

Some participants note that the complexity of problems often requires careful consideration of multiple variables and principles, which can be time-consuming. The discussion highlights the challenge of applying general principles to a variety of situations in physics exams.

-Dragoon-
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How exactly would be the best method in approaching them? It is not so much solving them that bothers me, but the fact that I am pressed for time. It becomes infeasible to draw diagrams, free-body/motion diagrams, listing knowns and unknowns, and then starting the analysis to solve 1 out of 13 problems with only one hour left. Any advice on this? How do you tackle problems in exams you've never seen before but yet don't have all the time in the world to solve them? Is it better in those cases to just mindlessly "plug-n-chug"?
 
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Which course are you taking?
 
jtbell said:
Which course are you taking?

Introductory physics I.
 
Practice, practice, practice, and more of it. I always begin by drawing a picture. A lot of the time this picture is merely a box, with force vectors acting on it. You'd be surprised how good you can get at drawing boxes.
Moreover, do you understand what is being asked? If you cannot absorb the question instantly, display an array of formulas that pertain to the particular problem, and asses the values that are given in the problem. Are all of these values relevant? What assumptions are being made?
Lastly, rest easy before an examination and eat healthy food. It takes practice to become good at these topics; some more than others, but nonetheless it takes practice.
 
Retribution said:
Is it better in those cases to just mindlessly "plug-n-chug"?

That depends whether you want to learn some physics, or just scrape through your exams.

But the "mindless" approach may not work anyway if you are being set good exam questions which test if you understood the material, and not just if you can memorize how to do the questions on last year's exam paper.

It could be that Mechanics is the first course you have taken where you need apply a few general principles to a large range of situations. You had better get used to doing that, because that's the way most of your courses will be from now on.
 
The more problems you practice the more you get a feel for what diagrams you need to draw, what variables you need to solve for, etc. You'll develop an intuition to the problems so that they amount to almost plugging and chugging since you'll know how everything fits together.


Im a bit confused, If you can solve the problem correctly by simply plugging and chugging then what's the problem. Why draw diagrams and list unknowns if you already know how to get to the answer?
 
sandy.bridge said:
Practice, practice, practice, and more of it. I always begin by drawing a picture. A lot of the time this picture is merely a box, with force vectors acting on it. You'd be surprised how good you can get at drawing boxes.
Moreover, do you understand what is being asked? If you cannot absorb the question instantly, display an array of formulas that pertain to the particular problem, and asses the values that are given in the problem. Are all of these values relevant? What assumptions are being made?
Lastly, rest easy before an examination and eat healthy food. It takes practice to become good at these topics; some more than others, but nonetheless it takes practice.

Again, drawing two diagrams for both objects and then two free-body diagrams can take major time away from the analysis of the question. Usually, these are the types problems that tend to be complex, problems with forces acting on two masses.

Eventually, working through so many dynamics problems, I am seeing a recurring pattern in which you have two equations and two unknowns and are constantly solving for those two unknowns, while some other variables cancel out. Wouldn't it be better to just use these shortcuts on exams rather than starting every question from scratch and writing out Newton's second and third laws for every component of every mass?
 
AlephZero said:
That depends whether you want to learn some physics, or just scrape through your exams.

But the "mindless" approach may not work anyway if you are being set good exam questions which test if you understood the material, and not just if you can memorize how to do the questions on last year's exam paper.

It could be that Mechanics is the first course you have taken where you need apply a few general principles to a large range of situations. You had better get used to doing that, because that's the way most of your courses will be from now on.

I enjoy working through problems and I have never "plugged-n-chugged" since high school. I'd even prefer exams with 4 very very difficult questions and work through them systematically, but unfortunately my exams are not structured like that. When you have 13 questions to get through, it is not feasible to draw diagrams for all of them and write out Newton's second and third laws and list the knowns and unknowns. That's what happened to me last time and is the main reason why I received such a low mark.
 

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