Edexcel 2024 Paper 3 Question 2 Solution (Mechanics)

Edexcel 2024 Paper 3 Question 2 – Speed-Time Graphs Explained

❓ The Question

💡 Teacher Explanation

Most people are fine with this at the beginning.

It’s just reading a graph. Nothing unusual. Straight line, steady increase, so you take a gradient and move on.

Where it becomes less straightforward is later. Not because the maths suddenly gets harder — it doesn’t — but because you have to start making decisions rather than just following a process.

The middle part is really just area. That idea is standard, but it’s easy to rush and miss something small.

The last part is the one that tends to trip people up. It looks similar to what came before, but it isn’t quite the same. If you don’t pause and check what shape you’re dealing with, it’s very easy to go down the wrong route.

So overall, nothing here is difficult on its own. It’s more about staying careful all the way through.

🎯 How To Recognise This Question Type

Speed-time graph → gradient gives acceleration, area gives distance.

🧠 Step By Step Solution

Start with the first section.

The speed goes from 0 to 10 in 4 seconds. Straight line, so constant acceleration.

$a = \frac{10}{4} = 2.5$

That’s the easy part.

If the object is at rest and you see “limiting equilibrium”, think maximum friction straight away.

Now deal with the distance up to 18 seconds.

Don’t overcomplicate it. Just split the graph.

First bit is a triangle:

$\frac{1}{2} \times 4 \times 10 = 20$

Then a rectangle:

$14 \times 10 = 140$

So total so far:

$160$

The full race is 200 m.

So there’s 40 m left for the final section.

$200 - 160 = 40$

Now — this is where you need to slow down slightly.

The last section slopes down, but it doesn’t go to zero. That matters.

So it’s not a triangle. It’s a trapezium.

$\frac{1}{2}(10 + U)\times 6 = 40$

Rearrange:

$(10 + U)\times 3 = 40$

$10 + U = \frac{40}{3}$

$U = \frac{10}{3}$

✅ Final Answer

(a) 2.5 m/s²
(b) 160 m
(c) $\frac{10}{3}$ m/s

🎯 Mark Scheme Breakdown

(a)

M1:
$\frac{10}{4}$ seen (correct gradient)
A1:
$2.5$ , $\frac{5}{2}$ or $\frac{10}{4}$ seen with units $\text{m s}^{-2}$

(b)

M1:
Area from $t=0$ to $t=18$ with correct structure seen
A1:
Valid area method clearly shown, e.g.
$\frac{1}{2}\times4\times10 + (14\times10)$ seen
(or equivalent trapezium / rectangle − triangle method)
A1:
$160$ with units $\text{m}$ seen

(c)

M1:
Uses area from $t=18$ to $t=24$ or
$200 – \text{their (b)}$ seen with correct structure
A1ft:
Correct method using consistent values (follow-through allowed), e.g.
trapezium / rectangle − triangle / suvat setup seen
A1:
$\frac{10}{3}$ or $3\frac{1}{3}$ seen

✅ Key Examiner Notes

“Seen” is critical — answers, structure, and methods must be explicitly written.
Units must be included:
acceleration → $\text{m s}^{-2}$ , distance → $\text{m}$
For area, the shape and structure must be visible, not implied.
Follow-through marks apply, but the working must still be valid and clearly shown.

Total: 8 marks

⚠️ Examiner Insight

Most students were comfortable at the start, but the drop-off came later in the question. The main issue was in the final section, where quite a few answers treated the region as a triangle. This changes the method completely, so no marks were awarded even if the final value looked reasonable.

This is really where most of the problem sits — once the wrong shape is assumed, everything that follows is built on the wrong structure. It often happens because the graph looks similar to earlier sections, so students move too quickly without checking properly.

A simple check is to look at the speeds at both ends of the interval. If both are non-zero, the region cannot be a triangle, so a trapezium (or equivalent method) must be used.

There were also some avoidable slips earlier on, particularly missing units in part (a). Even when the value is correct, the mark is not secured without $\text{m s}^{-2}$ .

This question is typically lost at the end rather than the beginning. A quick pause to decide what each section actually represents — triangle, rectangle, or trapezium — can prevent most errors and secure the method marks.

💬 Need help with questions like this?

It’s quite normal to be fine with the topic, then hesitate when it all shows up together.

Going over similar questions with an online A Level Maths tutor can help you get used to that. After a while, they start to look more familiar.

🔗 Next Steps

← Question 1
→ Question 3

👨‍🏫Author Bio

S Mahandru is a maths tutor who focuses on helping A Level students make their working clearer, so they can pick up the marks that are often missed.

📊 Final Summary

✅ Do This	❌ Avoid This
Use gradient first	Guessing
Split the graph	Treating as one shape
Check final section	Assuming triangle
Keep answers clear	Rushing

❓ Frequently Asked Questions

📌 Do I always use area here?

Yes. That’s how distance is found on a speed-time graph. Once you see the graph, that’s what you should be thinking.

📌 Why isn’t the last section a triangle?

It doesn’t go down to zero speed. So it can’t be a triangle — both values matter.

📌 Where do most mistakes happen?

Usually right at the end. The setup is fine, then something small goes wrong.

📌 Do units matter?

Yes, they do. Especially for acceleration — easy to miss if you rush.