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
Newton's first law
- 3 things to know
- Paper 5 (Physics)
Overview
What happens to an object with no resultant force on it, what a resultant force can change, and why spacecraft, books, cyclists and sliding loads behave as they do.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
State the law that describes what happens to an object when no resultant force acts on it.
Key term
What is meant by a resultant force?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the law that describes what happens to an object when no resultant force acts on it.
Model answer
An object stays at rest, or keeps moving at a constant velocity, unless a resultant force acts on it.
- 2
What is meant by a resultant force?
Model answer
The single force that would have the same effect as all the forces acting on an object combined.
- 3
A car travels at a steady 25 m/s along a straight road. What can be said about the forces acting on it?
Model answer
They must be balanced, so the resultant force on the car is zero.
- 4
What three changes to an object's motion can a resultant force produce?
Model answer
It can make the object speed up, slow down, or change direction.
- 5
A spacecraft far from any star switches off its engines. What happens to its motion, and why?
Model answer
It keeps travelling at a constant velocity in a straight line, because no resultant force acts on it.
- 6
Why does a book left alone on a table stay exactly where it is?
Model answer
The downward pull of gravity is matched by the upward push of the table, so there is no resultant force to move it.
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