Key term
OCR GCSE Physics A J249
Electricity
Topic overviewCharge, and producing static electricityTransfer of electrons, and electric fieldsCurrent as a rate of flow of chargeCharge, current and timeSeries and parallel circuits, and circuit symbolsCurrent, potential difference and resistanceResistors whose resistance changes, and investigating themLinear and non-linear circuit elements from graphsNet resistance in series and parallelCircuits for measurement, and electrical power
Energy
Topic overviewConservation of energy, and energy storesEnergy changes on heating, and calculating themEnergy of a moving body, a spring and a raised objectDissipation, and energy transfer in domestic devicesPower ratings, and calculating efficiencyReducing unwanted energy transfer, and the rate of cooling
Forces
Topic overviewMeasuring distance and time, and calculating speedConverting units, and ratesVectors and scalars in motionDistance-time and velocity-time graphsAverage speed, and the equations of uniform motionHow objects interact, and forces as vectorsNewton's first lawNewton's second lawForce and the time taken to change velocityWork done, and stored energyPower, and Newton's third lawStretching, bending and compressing; elastic and plasticForce and extension, linear and non-linearThe spring constant, and work done in stretchingGravitational fields, weight and free fallCalculations with weight and gravitational field strengthTurning forces and the moment of a forceLevers and gearsPressure in fluids, and the force on a surface
Global Challenges
Topic overviewTypical speeds and everyday accelerationsReaction time, stopping distance and the dangers of large decelerationsEstimating stopping distances and the forces in a collisionEnergy resources, and trends in their useThe national grid, and step-up and step-down transformersWhy the national grid is efficient, and power in a transformerMains electricity: a.c., d.c. and the domestic supplyLive, neutral and earth wires, and electrical dangerRed-shift and the Big BangThe formation of the Sun, and radiation from bodiesThe solar system
Magnetism and Magnetic Fields
Matter
Topic overviewHow the atomic model changed, and the structure of the atomThe size of atoms, and defining densityDensity of the states of matter, and density calculationsConservation of mass in changes of stateHeating a system, and specific heat capacityCalculations with specific heat capacity and latent heatGas molecules, temperature and pressureCompressing a gas, and changing its volumeAtmospheric pressure and why it varies with height
Radioactivity
Topic overviewProtons, neutrons and isotopesUnstable nuclei and the emissions they give outBalancing nuclear equationsElectron energy levels, and radiation from atomsHalf-life and the randomness of decayPenetration of alpha, beta and gammaContamination and irradiation, and half-life as a hazardUses of nuclear radiationNuclear fission and fusion
Waves in Matter
Topic overviewAmplitude, wavelength, frequency and periodThe wave equationTransverse and longitudinal wavesSound crossing a boundary; reflection, transmission and absorptionModelling waves with ripples and soundElectromagnetic waves as transverse, and energy transferFrequency and wavelength across the spectrumWhat our eyes detect, and light as an electromagnetic waveUses of electromagnetic wavesHazards of ultraviolet, X-rays and gamma raysRay diagrams for reflection and refractionHow colour arises
Forces
Newton's second law
- 2 things to know
- Paper 1
Overview
The relationship between resultant force, mass and acceleration, what one newton means, calculations of force, mass and acceleration for trolleys, cars and balls, and why a loaded lorry accelerates more slowly than an empty one under the same driving force.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What is the unit of force, and what does one of it mean in terms of mass and acceleration?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the relationship between the resultant force on an object, its mass and its acceleration.
Model answer
Resultant force = mass × acceleration.
- 2
What is the unit of force, and what does one of it mean in terms of mass and acceleration?
Model answer
The newton, and 1 N is the force that gives a mass of 1 kg an acceleration of 1 m/s².
- 3
A resultant force of 60 N acts on a mass of 15 kg. What acceleration is produced?
Model answer
60 ÷ 15 = 4 m/s².
- 4
What resultant force is needed to give a 1200 kg car an acceleration of 2.5 m/s²?
Model answer
1200 × 2.5 = 3000 N.
- 5
A resultant force of 24 N gives an object an acceleration of 3 m/s². What is its mass?
Model answer
24 ÷ 3 = 8 kg.
- 6
Two trolleys are given the same resultant force but one has twice the mass of the other. How do their accelerations compare?
Model answer
The heavier trolley accelerates half as much as the lighter one.
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