Common Mistakes to avoid during problem solving for IOAA /BDOAA

bdoaaadmin/ April 22, 2020/ Uncategorized/ 0 comments

Common Mistakes to avoid during problem solving for IOAA/BDOAA

So we revisited all the past papers and a few articles from the University of Virginia (Astrophysics Dept) and found a few common mistakes we should avoid during problem-solving.

Theory

1. Illogical conclusion unrelated to the question (e.g. damaging buildings)

Situation: Suppose a problem deals with Newtonian mechanics but you implement relativistic properties there. Considering the size and distance to the observer this approach may be illogical. Some participants brought in unnecessary special relativistic formula (Don’t show you know a lot. In IOAA you would not have to solve GR problems anyway)

Situation: The redshift z is simply the ratio of the shift in wavelength \Delta \lambda to the emitted wavelength lambda, \lambda .

z = \frac{\Delta \lambda}{\lambda} = \frac{v}{c}

So use general formula otherwise told to use the relativistic one.

2. Poor mathematical manipulation

Missing out terms, exponents, powers, or symbols in the flow of the problem! For large algebra or equation solving, students often miss out on simple letters/symbols or notations.

3. Dimensionally inconsistent equations and expressions

Do not underestimate dimensional analysis. And equating two sides of the equation with irrelevant dimensions or dimensionless property.

4. Introduction of new variables not described in the question without proper definition

Situation: For a geometry, where maybe an angle θ is already defined but still introducing new angle Φ without properly mentioning. Also using unconventional notations where there is a conventional notation is used widely such as using β to denote the Declination of the object (where δ is widely used).

These are the mistakes that a majority of students make but don’t know that they are actually making them. In this case, students tend to forget the necessary values. This happens because they do not have a piece of detailed knowledge of standard values.

5. Guessing an answer without quantitative proof nets zero marks

Situation: Guessing the angular size of an object where it can be calculated with precision to certain significant digits. Guessing a stars’ apparent Magnitude without comparing.

6. Equations are not written out in full with variables – marks will be lost as markers have to guess your meaning

Jumping through several lines without proper clarification or pre proposed solution.

7. Unit conversion

Unit conversion is a highly important aspect that most students forget to implement when given a problem to solve. If you fail to read the instructions properly, you will not get the actual result. Even if your problem solution procedure is correct, a mistake in unit conversion will show an incorrect answer. You can see such issues in case of solving problems on acceleration or force. The equation for arc length s = rθ requires θ to be in radians.

8. Not simplifying the expression to obtain the final answer

Sometimes student forgets to state the final answers in proper units stated to provide in the final answer.

Situation: Not converting kilometers to R⊙/AU/Parsec or Jouls to L⊙ or ergs.

9. Incorrect coefficient of the log term

Not using proper first-order approximations and making equations critical. Using logarithms where it can be simplified using natural logs (or ln). In Pogson’s law; it is 2.5, not 2.512 or  100^{1/5}

10: Constant correction or inability to draw figures

There are 2 scenarios with respect to drawing figures in Astro/physics. One is either you feel too lazy to see the entire diagrammatic description and make mistakes while drawing them. The other case can be using a pen instead of a pencil to draw and explain the diagram. In both cases, the entire presentation of your problem or assignment looks shoddy. Ruining all your efforts of work execution, this mistake can be one of the main reasons for your grade reduction.
Lookout for wrong pointing arrows or rays.

In IOAA almost 20% mark is given for proper geometry and detailed explanation

11. Some candidates treated the proportionality relations as equations

 F = \frac{L}{4\pi d^2}

 F \propto \frac{1}{d^2}

but can’t be written as-  F = \frac{1}{d^2}

12. Mixing Laws/Theories/Postulate and Assumptions

The Hubble constant is in fact, the value of the Hubble parameter at the current epoch; its value changes with the evolution of the Universe. The standard assumption is the Universe is Isotropic you can’t treat this as a fact.

13. Printing Mistakes

Making errors during typing the values in the calculator or printing out the wrong digits or missing/adding a few digits. Forgetting to convert kilometers to meters for the SI unit.

Observation/Practical

  • Estimates of the latitude using linear proportion without correcting for the error of stereographic projections (generally falling around 30-40 degrees)

  • CE is not a smooth arc (e.g. horizontal line, vertical line, abstract curves) or is a closed trace

  • Points are plotted correctly with decent use of space (minimally 70% of the area of graph paper)

  • Axes are correctly labeled with units

  • The graph is properly titled with units

  • Best-fit trend lines are drawn. All other curves (quadratic, exponential) score no credit.

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