Key term
CCEA AS-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Topic overviewResistance and Ohm's lawOhmic and non-ohmic behaviourResistors in series and in parallelInvestigating current, voltage and resistance in series and parallel circuitsElectrical power and energy in resistive circuitsResistivity and the equation R = ρl/AMeasuring the resistivity of a metalCurrent–voltage characteristics of a conductor, a lamp and a diodeResistance, temperature and superconductivity
Internal Resistance and Potential Dividers
Topic overviewInternal resistance and terminal potential differenceConsequences of internal resistance for external circuitsMeasuring electromotive force and internal resistanceThe potential divider and variable outputPotential dividers in lighting and heating control circuitsLoaded potential dividers and output voltage calculations
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Topic overviewSuperposition of wavesStanding waves, nodes and antinodesStanding waves on stretched stringsStanding waves in a pipe closed at one endMeasuring the speed of sound with a resonance tubeConditions for observable interferencePath difference and phase differenceYoung's double slitDiffraction at a single slitThe diffraction grating
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Topic overviewChoosing and using measuring instrumentsPrecision, accuracy and recording measurementsUsing the cathode ray oscilloscope to measure voltage and frequencyTables, graphs and presenting resultsLinearising a relationship and using the gradientAbsolute and percentage uncertaintyCombining uncertainties and uncertainty on a graphRandom and systematic error, reliability and refining an experiment
Moments and Equilibrium
- 4 subtopics
- 12 things to know
- Unit AS 1
What Moments and Equilibrium covers
Moments and Equilibrium is examined in Unit AS 1, Forces, Energy and Electricity, and drawn on again in Unit AS 3, Practical Techniques and Data Analysis. It covers moment of a force, centre of gravity, the principle of moments and determining unknown masses using moments.
Where it is assessed
Unit AS 1
Forces, Energy and Electricity, and again in Unit AS 3, Practical Techniques and Data Analysis.
Check the CCEA specification ↗The 4 subtopics
Each one has its own page. CCEA AS Physics students sit this topic in the first year.
- Moment of a forceRecall questions on the definition of a moment and its equation, why the unit is the newton metre and not the joule, why the perpendicular distance is used, the moment of a force through the pivot, the spanner and door handle examples, and calculations with a force at an angle to the lever.Open →
- Centre of gravityCentre of gravity of an object and condition under which a tilted object will topple.Open →
- The principle of momentsRecall questions on the statement of the principle, the two conditions for a rigid body in equilibrium, choosing the point to take moments about so an unknown reaction drops out, and worked problems on a seesaw, a plank on two supports, a hinged beam and a wheelbarrow.Open →
- Determining unknown masses using momentsRecall questions on balancing a metre rule to find an unknown mass, why it is first balanced at its centre of gravity, why masses need not be converted to weights, finding the mass of the rule itself by moving the pivot, the main sources of uncertainty, and why several known masses are used.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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Describe how the centre of gravity of an irregular flat lamina is found in the laboratory.
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Explain the effect on a bus's stability of filling the upper deck with passengers while the lower deck stays empty.
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Distinguish between the centre of mass and the centre of gravity of an object.
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Describe how the principle of moments is used to determine an unknown mass with a metre rule.
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Describe how the mass of a uniform metre rule is determined using the principle of moments.
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State the two conditions that must both be satisfied for a rigid body acted on by coplanar forces to be in equilibrium.
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State the equation for the moment of a force, defining each symbol and its unit.
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Explain why the clockwise and anticlockwise moments in the principle of moments must be taken about the same point.
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State the moment of a force whose line of action passes through the pivot.
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Explain why a body can have zero resultant force acting on it and still not be in equilibrium.
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Explain why the pivot must be moved away from the centre when the mass of a uniform rule is being found.
Take Moments and Equilibrium further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
Define the moment of a force about a point.
Model answer
The moment of a force about a point is the product of the force and the perpendicular distance from that point to the line of action of the force.
- 2
State the equation for the moment of a force, defining each symbol and its unit.
Model answer
The moment is M = Fd, where M is the moment in newton metres (N m), F is the force in newtons (N) and d is the perpendicular distance in metres (m) from the point to the line of action of F.
- 3
Give the unit of a moment and explain why it is not written as a joule even though it is also a newton metre.
Model answer
The unit is the newton metre (N m); the joule is reserved for energy, which is a force multiplied by a distance moved in the direction of the force, whereas a moment uses a distance measured at right angles to the force.
- 4
What must be stated alongside the size of a moment, and why?
Model answer
The sense of the moment must be stated as clockwise or anticlockwise, because two moments of the same size in opposite senses cancel rather than add.
- 5
Name the two factors that determine the turning effect of a force about a point.
Model answer
The turning effect depends on the magnitude of the force and on the perpendicular distance from the point to the line of action of that force.
- 6
Why is the perpendicular distance used in calculating a moment rather than the distance from the pivot to the point where the force is applied?
Model answer
Only the component of the force at right angles to the line joining the pivot to the point of application produces turning, and using the perpendicular distance from the pivot to the line of action gives exactly that turning effect.
What is inside Levo
Six ways to work the same material.
Moments and Equilibrium revision questions
- Is Moments and Equilibrium examined at AS in CCEA Physics?
- Yes. It sits in Unit AS 1, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.
- What does Moments and Equilibrium cover in CCEA AS-Level Physics?
- 4 subtopics: moment of a force, centre of gravity, the principle of moments and determining unknown masses using moments. Each one has its own page with questions and model answers.
- How is Moments and Equilibrium organised?
- By the CCEA 1210 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Moments and Equilibrium, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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