Physicists - what do you think of this question?

[hotchococlock]

This is a question from DC's A level physics homework on the topic of Force Equilibrium. There's no further context given.

We think the strange blobs in the blue diagram may be cars, and the lines may be parts of a bridge, but we're open to other interpretations. 🙂

How would you tackle it?

I agree. Part of a suspension bridge with the supports shown.
Poor question!

Terrible drawing. Is the vertical line from x a column or a string? Makes all the difference 😅

Go ven no further interpretation, C would be the logical choice, but I failed A level physics so…

The correct answer is B, because that's the one that turns green rather than red when it is selected, though it's not clear why B is the "third force" rather than the "second force."

Presumably the weight is the "first force" (since it was mentioned first) and acts down the vertical line that looks like it could be the leg of the bridge. Though I do hope the bridge has another leg that also bears some of the weight. 🙂

That would make D the "second force", for what it's worth.

Actually, no, I think the "Second force" must be the non-vertical line that meets X.

This might be the logic for the numbering (but, if so, I'm not sure why the third force "acts at X", other than because I know the forces need to be balanced) ...

I’d be embarrassed to set a question like that. I teach a-level mechanics and have no clue what they’re trying to get across with that horrible picture. I think you’re right that they’ve tried to do a resolution of forces question, but what’s the point without any angles or actual forces being drawn? I’d have thought personally that you’d need a force acting vertically upwards at x for the normal reaction, but they don’t seem to have included this.

I’d advise him to move past it, say what the teacher requires, and maybe watch a video from mathsgenie on the topic instead. I’m presuming the teacher is trying to work on something like this topic:

https://www.mathsgenie.co.uk/a-level-mechanics-and-statistics-moments.html

mathsgenie is great. The mechanics section should cover a lot of material from the physics course.

Sorry, I forgot to remove this image (but this is what a force diagram should look like!)

Thanks @Nellodee . Yes, many of the questions in the school's extensive question bank are of similarly poor quality, and they're not so easy to move on from because they're used for homework and tests.

I will have a look at Mathsgenie - thanks for the tip!

I know absolutely nothing about Physics, though my DS1 is also in his first year of A level, and I'm even worse at drawing than the creator of this question - I also struggle to understand diagrams etc. Do real questions tests students on this level of ambiguity? However, several of you have mentioned that there should be other details on the diagram, and I note that the second sentence of the question asks the student to "draw in a third force".

Do real questions tests students on this level of ambiguity?

No, this style of question is unique to a particular school. It's not A Level format.