Edexcel 2024 Paper 3 Question 1 Solution (Mechanics)

Edexcel 2024 Paper 3 Question 1 – Forces & Friction Explained

❓ The Question

💡 Struggling with questions like this?

If questions like this feel difficult to approach, it’s often because multiple ideas are being tested at once. Without a clear strategy, it’s easy to lose marks even if you understand the topic.

Working through a structured A Level Maths revision course can help you build confidence, improve exam technique, and recognise patterns across different question types.

🧠 TEACHER EXPLANATION

This is one of those questions that looks almost too simple — and that’s usually where marks get dropped.

Nothing complicated is happening here. The particle isn’t moving, so everything is balanced. That’s the starting point. If you keep that idea clear in your head, the rest follows quite quickly.

In part (a), you’re just dealing with vertical forces. There’s no trick — the surface is flat, so the normal reaction simply balances the weight.

Part (b) is where students sometimes hesitate. The phrase “limiting equilibrium” is doing all the work. It tells you that friction is at its maximum value, so you can go straight to the standard relationship.

It’s not a long question, but it’s a good check of whether you’re comfortable with the basics.

🎯 How To Recognise This Question Type

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

✏️ Working

Step 1: Look at vertical forces

The particle is not moving, so vertical forces must balance.

Weight acts downwards and the normal reaction acts upwards.

$R = 0.5g$

Substitute the value of gravity:

$R = 0.5 \times 9.8 = 4.9$

Step 2: Use the idea of limiting friction

At limiting equilibrium, friction takes its largest possible value.

$F = \mu R$

Step 3: Substitute the values

$F = \frac{2}{7} \times 4.9$

$F = 1.4$

Step 4: Balance horizontal forces

The particle is still in equilibrium, so the applied force must match the friction.

$X = 1.4$

✅ FINAL ANSWER

(a) 4.9 N
(b) 1.4 N

🎯 Mark Scheme Breakdown

B1:
$0.5g$ , $\frac{1}{2}g$ or $4.9$ seen
M1:
$\frac{2}{7} \times 4.9$ seen
(or equivalent method using $F = \mu R$ with correct substitution)
A1:
$1.4$ or $1.40$ or $\frac{1}{7}g$ seen

✅ Key Examiner Notes

The word “seen” is critical — the value must be explicitly written, not implied.
For M1, a clear method must be shown (not just a final answer).
For A1, the answer must match one of the accepted forms and be clearly stated.

Total: 3 marks

⚠️ Examiner Insight

This question was answered well by most students, and many picked up all the marks. Where marks were lost, it wasn’t because the maths was difficult — it came down to clarity and finishing the job properly.

A common issue was calculating the friction but not explicitly linking it to the applied force. In limiting equilibrium, the friction is equal to the applied force, and that connection must be clearly stated. Some students also made small slips with values such as $g$ , which is easy to avoid with a quick check.

Another place marks were dropped was stopping too early. Getting the friction is not the final answer — the question asks for the applied force, so it must be written clearly at the end.

A frequent mistake is treating mass as weight. This usually happens when rushing early questions. Always write weight as $mg$ before substituting numbers to keep the method clear.

Overall, this is the kind of question where students lose marks by being slightly too casual. It looks straightforward, so steps get skipped. Stay precise, state the final answer clearly, and when you see “limiting equilibrium”, go straight to maximum friction.

💬 Need help with questions like this?

If this type of question feels slow, it’s usually not the maths. It’s just not being sure where to begin, especially when everything is in one place.

Working through a few like this with an A Level Maths tutor can help with that. It just makes the starting point clearer, which is usually where things go wrong.

🔗 Next Steps

← Paper Overview
→ Question 2 Solution

👨‍🏫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
$R = mg$	Mixing up mass and weight
$F = \mu R$	Guessing friction
State final answer clearly	Leaving it implied
Keep working tidy	Rushing

❓ Frequently Asked Questions

📌 When do I use friction equals mu times R?

Only when it’s right on the point of moving. That’s usually when the question says limiting equilibrium, so friction is at its largest value.

📌 Why does the normal reaction equal the weight here?

Nothing else is acting vertically, so it just balances. There isn’t anything extra to think about in that direction.

📌 Does the value of gravity really matter?

Yes — you should stick to 9.8 unless told otherwise. Using something like 9.81 can throw the final answer off slightly.

📌 Why do people lose marks on this question?

It’s usually small things. Skipping a step, or not clearly stating the final answer, tends to be where marks go.