# GCSE Level Questions: Moments and Centre of Gravity

When answering a question that has sub-parts ((i), (ii), (iii) etc.) look at what is needed in ALL parts before formulating your answer.

You will not get marks for making the same point in both parts.

Also reading the whole section of the question helps you understand where the examiner is 'going' with the question.... what information s/he is trying to get out of you for the mark...

### General Pointers - Things to think about before attempting these questions

Centre of mass is the same as centre of gravity. It is the point through which the weight of the object acts.

You draw the weight arrow vertically down from that point.

If an object is made up of various parts and you move one of those parts the centre of mass/gravity of the whole thing will move position - and that may affect the overall stability.

NEVER use the word momentum instead of moment – they are quite different!

A point can never be parallel or perpendicular to anything!

A moment has two parts – if the moment is greater that can be due to either part. Therefore if a moment is 'greater' it is wrong to say ‘the force of the moment increases’ unless you are talking about the ‘force part’ of the moment.

A resultant moment will cause an object to turn – a resultant force will produce an acceleration (F = ma) 'm' is the abbreviation for mass NOT the abbreviation for moment!

Always write the word 'moment' for a moment - never abbreviate it to 'm' or 'M' unless your syllabus allows you to do so!

 Click on a question number to view one of the following questions - a rough guide to content is given to help you choose! A solution to each question is linked from the question page. The mark scheme is in red; and comments to help you understand why the marks are awarded in that way are in green. Click here to go to the notes on moments

 Q1. 6 marks Stability of a computer monitor. Q2. 6 marks Stability of a mobile crane Q3. 6 marks Child's mobile and the stability of a ladder - device to increase the stability Q4. 5 marks Using a spanner Q5. 5 marks Lampshade Q6. 8 marks Fork-lift truck Q7. 9 marks See-saw Q8. 5 marks Centre of mass and oscillations Q9. 7 marks Drum kit moments Q10. 5 marks Centre of mass - block stacking Q11. 8 marks Stability of bus - also hydraulics Q12. 8 marks Opening a lorry ramp door Q13. 12 marks A balance to weigh rice Q14. 3 marks Pedalling a cycle.