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146 Cards in this Set
- Front
- Back
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Define the resultant force... |
The sum of all forces. |
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When the resultant force is 0... |
The object is moving at a steady speed |
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The unit of acceleration |
m/s^2 |
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Forces on a parachutist? |
Air resistance, weight. |
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What do you do to a spring to stretch it |
Work |
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What is work in physics |
Energy transfered |
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What is Hooke's law? |
The extension of an elastic object is directly proportional to the force applied, provided the limit of proportionality is not exceeded. |
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What is is force measured in? |
Newtons(N) |
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Work means energy transferred in... |
Joules(J) |
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What is time is measured in... |
Seconds |
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What is power measured in? |
Watts(W) |
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Unit for kinetic energy... |
J |
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Unit for mass... |
kg |
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Unit for velocity... |
m/s |
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Unit for gravitational field strength... |
N/kg |
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What are the units for weight and mass... |
Kg |
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Unit for momentum... |
kg m/s |
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Conservation of momentum... |
The total momentum before an event is equal to that after it. |
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The longer the impact time... |
the more the impact force is reduced
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Time taken for driver to react |
Thinking distance |
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Time take for car to stop after the brakes have been applied |
Braking distance |
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Time taken for car to stop |
Stopping distance |
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What increases thinking distance? |
Tired Under influence |
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What increases braking distance |
Ice/wet roads Bad tires |
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What happens if a polythene rod is rubbed by a dry cloth? |
Both may become electrically charged |
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A positively and negatively charged object will be... |
Attracted |
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What causes static electricity |
The movement of electrons on to an insulator |
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Open Switch |
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Closed Switch
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Lamp
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Cell
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Battery
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Voltmeter
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Resistor
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Fuse |
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Ammeter
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Variable Resistor
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Thermistor
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Light Dependent Resistor LDR
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Light Emitting Diode LED
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Diode |
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1 coulomb in 1 second = |
1 amp
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What is charge measured in |
Coulombs |
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What is potential difference measured in? |
Volts |
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Across a fixed resister when the temperature is constant |
Potential difference across a resister is directly proportional to the potential difference |
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Measure of resistance |
Ohms |
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Measure of current |
Amps |
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Total resistance is.. |
the sum of resistance of all individual resistors or components |
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What are the rules of series circuits |
The total resistance is the sum of resistance of all individual resistors or components The components share p.d. Current is the same everywhere p.d. off cells is sum of individual cells |
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What are the rules of parallel circuits |
The p.d. across each component is the same The current is different in different branches of the circuit Currents add up |
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The higher the resistance... |
...the lower the current |
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For an LDR... |
The higher the light intensity, the lower the resistance |
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For a thermistor... |
The higher the temperature, the lower the resistance |
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What is the difference in efficiency between an LED and a filament lamp |
Lamp is about 7X more efficient |
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Describe a fixed resistor graph |
Linear |
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Describe a lamp graph |
Curved |
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Describe a diode graph |
Positive values only |
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Why does raising the temperature effect the resistance of a conductor |
Free electrons flow As the metal gets hotter the ions gain energy Causes the ions to vibrate more Electrons collide more often Restricting the current that can flow |
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Name the two types of household electricity |
AC and DC |
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What is the number of cycles per seconds in AC called |
The frequency |
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What are the characteristics of mains electricity in the UK |
AC P.D. = 230V Frequency = 50Hz |
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How to calculate frequency |
1/time taken for 1 cycle |
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What is a cable with 3 wires called |
Three core cable |
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How plugs are safe |
Case made of a tough, good insulator Cable grip to hold cable in place Fuse - melts if current is too high |
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How does an earth wire work |
Live wire causes low resistance resulting in high current which blows the fuse |
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What is an RCCB |
Residual current circuit breaker |
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How does an RCCB work |
Detects small differences in current and switched off the circuit straight away Can be reset and cuts of current faster than a fuse |
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When a current flows through a thin wire |
It will get very warm |
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Thin wires produce more ... verses thick wires |
Resistance or heat |
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CFLs are ... than filament lamps |
more efficient |
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Unit for power |
Watts |
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Unit for energy transfered |
Joules |
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How to calculate the fuse to use |
Power rating / voltage` |
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Definition of p.d. |
Amount of energy per coulomb of charge |
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Definition of charge |
Amount of coulombs |
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Instrument used to measure radioativity |
Geiger tuber (counts per minuet) |
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What is background radiation |
Naturally occurring radiation Air (Radon gas) (50%) Food and drink Rocks and ground Cosmic rays Nuclear accidents |
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How did Rutherford and Marsden find the structure of the atom |
Fired a stream of alpha particles towards thin gold foil Detector used and found that some alpha particles were deflected In a vacuum |
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Where does radiation come from |
The nucleus of an atom |
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What is alpha radiation composed of |
2 neutrons and 2 protons (Helium nucleus) |
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What is beta radiation composed of |
An electron that is ejected from the nucleus as a neutron breaks down |
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What is gamma radiation composed of |
Electromagnetic wave |
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Alpha particle range in air and stopped by... |
Few centimeters Paper or skin |
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Beta particle range in air and stopped by... |
Few mm of aluminium |
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Gamma particle range in air and stopped by... |
Few cm of lead or a few feet of concrete |
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Describe the deflection of radioactive particles in a magnetic and elecric field |
Beta is deflected the most Alpha is deflected slightly Gamma ray is not deflected |
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What is the most ionising radiation? |
Alpha |
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Gamma uses |
Sterilize Kill cancer cells tracers |
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Alpha usues |
Controlling paper thickness Smoke alarms |
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Beta uses |
Controlling foil thickness |
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What nuclear process happens in a nuclear power station |
Nuclear Fission |
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Elements used in nuclear power stations |
Uranium-235 Plutonium-239 |
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What are uranium and plutonium known as? |
A fissionable element |
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Describe nuclear fission |
An electron fired into a nucleus Nucleus split and energy and three neutrons released in a chain reaction |
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Nuclear fission recap |
Splitting of the nucleus |
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Where does nuclear fusion happen? |
In stars because of heat and gravity |
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What is nuclear fusion |
Joining of small nuclei releasing energy and no radioactive waste |
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Describe the life cycle of stars roughly the size of the sun |
Protostar Main Sequence star Red Giant White dwarf Black dwarf |
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Describe the life cycle of stars bigger than the sun |
Protostar Main Sequence star Red super giant Supernova (scatters elements throughout the universe) Neutron star or a black hole |
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X rays can cause what |
Ionisation Affect photographic film like light Absorbed in metal and bones |
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How to protect against X-rays |
Lead shielding
Film badges |
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What is a CCD |
Charge coupled device |
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CT scanners vs XRay machines |
CT: High dose 3D image Distinguish between soft and hard tissues X-Ray Lower dose 2D image Cheaper |
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Range of human hearing |
20Hz - 20,000Hz |
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Define ultrasound |
Sound with a frequency higher than 20,000Hz |
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How does ultrasound work |
Waves partially reflected when different media is met Time taken for reflections measured by detector An image is produced |
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Measurement of meters |
Meters |
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Uses of ultrasound |
Prenatal scanning Treat kidney stones Measuring the speed of blood flow in the body |
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Pros of ultrasound |
non-ionising Produce accurate images of soft tissue |
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What is the normal line |
line perpendicular to the medium |
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What is the angle of incidence and the angle of refraction |
Angle light enters to the normal line and angle light exits to the normal line |
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Structure of the eye |
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Short sight... |
Long egeball, concave lense |
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How a camera works... |
Converging lens fixed focus Focus achieved by varying lens position Image focused on film or CCD Brightness controlled by aperture REAL, INVERTED, DIMINISHED |
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How eye works... |
Converging lens variable focus Focus achieved by contraction of ciliary muscle Image focused on to retina Brightness controlled by iris and pupil REAL, INVERTED, DIMINISHED |
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Lens power is measured in... |
Dioptres |
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For a concave lens the lens power is... |
negative |
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Changing the material of a lens can affect the... |
Refractive index |
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The angle at which a light ray travels between the two mediums |
Critical angle |
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Application of TIR
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Endoscope for keyhole surgery Super fast internet |
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Lasers |
Intense and monochromatic light Used for quartering Cutting Burning Laser eye surgury |
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What is the center of mass |
The point at which the mass of an object may thought to be concentrated |
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Where is the center of mass |
Directly below the point of suspension |
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How to find the center of mass of an object |
Use a plumb line |
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What is a moment? |
A turning effect of a force |
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What is a lever? |
A force multiptier |
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What is the unit of moment |
Nm (Newton meters) |
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If an object is balanced |
The anticlockwise moment = the clockwise moment |
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When the clockwise moment is larger than the anticlockwise moment |
It becomes unbalanced |
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An object becomes unstable when... |
The line of action of the weight lies outside the base, there will be a resulting turning force and the object will topple |
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Why do hydraulics work |
Liquids are virtually compressible. |
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What is the area of hydraulics measured in |
square metres |
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What is pressure measured in? |
Pascals |
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Without a centripetal force... |
The object would fly off in a straight line |
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An object moving in a circle |
Accelerates towards the centre, directions constantly changes but not speed Resultant force is centripetal force which causes the acceleration. Centripetal force needed increases if: The mass increases The speed increases the radius decreases |
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When current is flowing through a wire... |
You get a magnetic field around the wire |
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To make a stronger electromagnet |
Add an iron core Increase current Increase coils |
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Purpose of a relay switch |
Low current circuit to switch on a high current circuit |
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Describe Flemings LHR |
Thumb - movement First finger - field Second finger- current |
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Force can be increased by increasing the (motor effect) .. |
Current Magnetic Field |
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The force can be reversed by (motor effect) ... |
Reversing the magnetic field Reversing the current |
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How does a transformer work |
Insulated wires with an A.C. This produces a changing magnetic field Which induces an alternating p.d. in the second wire And therefore produces an A.C. in the second wire |
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More coils in the secondary that primary |
Increases the voltage (step up) |
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More coils in the primary than secondary |
decreases the voltage (step down) |
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If a transformer is 100% efficient... |
The power is the same on both sides |
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What is the name of a more efficient transformer? |
Switch mode |
