Key term
OCR GCSE Combined Science Physics J250
Electricity
Topic overviewCharge, and producing static electricityTransfer of electrons in charging and dischargingCurrent 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 lawWork 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 strength
Global Challenges
Topic overviewTypical speeds and everyday accelerationsReaction time, stopping distance and the dangers of large decelerationsStopping distance, acceleration and collision force calculationsEnergy 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 danger
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 pressure
Radioactivity
Waves in Matter
Topic overviewAmplitude, wavelength, frequency and periodThe wave equationTransverse and longitudinal wavesModelling 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 raysInvestigating reflection and refraction of light
Forces
Work done, and stored energy
- 3 things to know
- Paper 5 (Physics)
Overview
How work done is calculated and its unit, why holding a bag still does no work, where energy goes when work is done against friction, and the energy in a moving object's kinetic store.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
What has happened, in terms of energy, when work is done on an object?
Key term
A force of 30 N pushes a box 6 m along a floor. How much work is done?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How is the work done by a force calculated?
Model answer
Force × distance moved in the direction of the force.
- 2
What is the unit of work done?
Model answer
The joule.
- 3
What has happened, in terms of energy, when work is done on an object?
Model answer
Energy has been transferred to the object by the force.
- 4
A force of 30 N pushes a box 6 m along a floor. How much work is done?
Model answer
30 × 6 = 180 J.
- 5
Why is no work done when a person simply holds a heavy bag still?
Model answer
The bag does not move along the line of the force, so the distance moved in that direction is zero.
- 6
An object is moved 15 m and 450 J of work is done. What force was applied along the direction of movement?
Model answer
450 ÷ 15 = 30 N.
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