Common Mistakes in the International Physics Olympiad
At the IPhO, small errors in reasoning or calculation can lead to a significant loss of points. Awareness of common pitfalls is the first step toward avoiding them.
Theoretical Paper Pitfalls
- Making an approximation without justification. State any assumption (e.g., small angles, non-relativistic speeds) and briefly explain why it is valid in the context.
- Losing track of variables in complex algebra. Perform dimensional analysis on your intermediate and final expressions to check for consistency.
- Deriving a correct formula but making a calculation error. Substitute values only at the last step; a correct symbolic answer earns most of the credit.
- Forgetting to check if the answer is physically reasonable. Test your final expression with simple or limiting cases to see if it behaves as expected.
- Providing only the final answer to a multi-step question. Write down your logical steps clearly, as partial credit is awarded for correct reasoning even if the end result is wrong.
Experimental Paper Pitfalls
- Recording raw data without estimating its uncertainty. For every measurement you take, write down both the value and your best estimate of its uncertainty.
- Plotting a graph without error bars. Represent the uncertainty of each data point visually using horizontal and vertical error bars.
- Drawing a 'line of best fit' by eye without a clear method. Use a systematic method, like calculating the line of best fit or using lines of maximal and minimal slope.
- Failing to explain the procedure and sources of error. Document your experimental method, justify your choices, and discuss the main sources of systematic and random error.