6 of the Commonest Mistakes Students Make While Solving Physics Numerical Problems

Many students consider physics numericals as an intengral part of their academic problems. They have more or less zero issues with the entire subject, but as soon as numerical problems crop up, the entire thing just goes right down the drain.

In this article, we’ll take a peek at a few of the most common mistakes that students make while solving physics numerical problems which, as a whole can severely affect their performance for bad.

Always remember, mistakes are NEVER a part of the problem. Not learning from them is. Hence, we hope you learn from the ones depicted below and strive to NOT repeat them in future. Anyway, let’s begin without further ado.

1. Answering in the wrong unit system

It’s a silly mistake that plagues almost every school and college in Australia.

The mistake usually takes shape in this fashion:

The numerical problem came with units in the MKS system but it wanted the final answer in the CGS. The student did everything right. S/He wrote the formula right, did the calculations well, scribbled down the answer, and that was where everything went downhill for him/her.

Did you forget? The problem wanted the answer in CGS. S/He never bothered to convert his/her answer (that came in MKS) to CGS. So the result’s ultimately zero even though s/he did almost the entire thing right.

Hence, it’s advisable to pay special attention to the question from the very first word to the last to ensure such silly mistakes don’t happen in exams.

2. Unit mix-up

Another common problem. Here’s an example for the sake of explanation:

The numerical problem provided students with two values that they would have to incorporate in their formula and come to a result. One was in CGS, and another one was in MKS. But the students didn’t pay much heed to the matter.

They took the values as it was, wrote the formula, made the calculations and came to the result. Overall performance result- ZERO!

Why? Because they failed to maintain consistency in units and hence, the result went wrong in the final stages of the solution.

Hence, a consistency of units MUST be maintained even in practice to ensure such mix-ups don’t happen in exams.

3. Confusing radians with degrees

Radians and degrees aren’t similar in any way whatsoever. A mix-up up will result in only one thing, and that is shown in the image below.

Most physics numerical problems usually use degrees from the general sense of view. But here’s a thing to remember- “NOT ALL.”

Case in point-

Angular velocity and acceleration. That’s exactly where you’ll have to remember that you are actually using radians in your calculations and hence, your calculations should be made on the basis of that.

Keep these things in your mind, and you’ll see that you have turned your problems into a part of your solution in almost no time.

4. Forgetting that there’s something called latent heat in thermodynamics

When you are involved in a problem that involves some sort of a phase change, like a change of state from ice to water, don’t forget that there’s something called the latent heat that you will have to incorporate into your calculations to get to the correct result.

Miss out and get a zero; it works as simple as that.

5. Incorrect resistor additions

One of the commonest mistakes that students make in solving a physics numerical problem lies in finding out the total resistance of a circuit.

Circuit depicting resistances in parallel

Source- Wiki

They mix up between parallel resistance and series resistance and calculate wrongly on the basis of that.

Here’s a thumb rule that you MUST remember,

• If two resistors (say, X1 and X2) are in series,

Total resistance (R)= X1 + X2.

• When two resistors (say, R1 and R2) are in parallel,

1/R= 1/X1 + 1/X2 (R-> Total resistance).

6. Mixing up sines with cosines

It’s a pretty fundamental problem in Physics, but it does happen a lot resulting in a poor overall performance.

Ensure that you know these by heart (don’t forget to refer to the image first):

Figure depicting a right-angled triangle

• sin θ = opp./hypotenuse= b/a.

• cos θ = adj./hypotenuse= c/a.

• tan θ = opp./adj. = b/c.

[opp.= opposite; adj.= adjacent]

So that’s pretty much it. Hope you find the article exceptionally handy for your exam preparations. With that, we’ll sign off finally for the day. Hope you had a great read.