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39 Cards in this Set
- Front
- Back
how is speed calculated |
speed(m/s)=distance(m)/time(s) time= distance/speed |
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what does the gradient of a distance-time graph represent |
speed the steeper the gradient the greater the speed a horizontal line represents stopped (no increase in distance) |
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what is velocity |
speed in a direction it is a vector quantity measured in m/s |
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what is acceleration |
the rate of change in a given direction measured in m/s2 accleleration = change in velocity/ time taken for change |
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what are the key features of a velocity-time graph |
are under the line= distance travelled(m) gradient = acceleration the steeper the gradient the greater the acceleration horizontal line means constant velocity unless the line is on the x-axis: means stopped |
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what can forces do to an object? |
change its shape change its motion (nb forces cause a change in motion-an object does not need force on it to be moving) |
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unbalanced forces result in |
a resultant force an acceleration (change in motion) f(n)= mass(kg)*acceleration(m/s2) mass= force/acceleration acceleration = force/mass
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balanced forces result in |
no acceleration (no change in velocity) |
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stopping distance is |
thinking distance + breaking distance nb: be careful to check whether the question discussing stopping distance or stopping time |
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factors whihc affect the thinking distance are |
related to the driver:tiredness, drugs, distractions speed of the car (does not affect the time just the distance travelled while thinking) |
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factors which affect the stopping distance are |
related to the car & conditions: weather, ice, effectiveness of the breaks speed of the car (does not affect the time just the distance travelled while stopping) |
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what is the difference between weight and mass? |
weight is force caused by gravity acting on a mass mass is a measure of the number of particles in an object weight(n)= strength of gravityn/kg)*mass(kg) |
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what are the forces on a falling object |
weight (down) and drag(up) |
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why do falling objects reach a terminal velocity |
as objects fall they accelerate. their weight stays the same but as they move faster the drag increases. the resultant forces reduces and so acceleration reduces eventually the drag force is equal and opposite to the weight (forces are balance) there is no acceleration this speed is terminal velocity |
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how is extention calculated |
extension=length- original length |
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what type of energy is stored ina spring |
elastic potential energy |
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hat is hookes law |
relates the force applied to a spring to its extention force(n)=spring constant (n/m)*extension(m) spring constant = force /extension the relationship between force and extension os directly proportional (a straight line on a graph through the origin_ |
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what is energy? how is it measured |
energy is the ability to work it is measured in joules
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how much energy is used moving on an object |
energy transferred=work done work done(j)=force*distance(m) force=work done/distance |
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how much energy is used moving an object upwards |
change in gpe(j)=weight (n)*change in height (m) change in gpe (j)= mass (kg) strength of gravity (n/kg) * change in hight |
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how is power related to energy |
rate of energy transfer power=energy/time |
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how is kinetic energy calculated |
ke= 0.5*mass*velocity2 mass=2xke/veloctiy |
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what is momentum |
a vector quantity related to the mass&velocity of a moving object momentum = mass *velocity |
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what is the law of conservation of momentum |
in a closed system momentum before an event=momentum after an event usually applied in collisions
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how does safety features such as helmets/rubber matting/ air bags work |
reduce the impact force for the same energy transfer/change in momentum increasing the distance/time over which the energy is transferred reduces the force force=energy/ distance force= change in momentum/ time taken |
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how is static electricity formed |
use of a force such as friction to separate charges in an insulator (they can't flow and recombine in an insulator) |
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what do opposite/ like charges do? |
opposite charges attract like charges repel
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what is an electric current |
the flow of charge |
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what flows through a circuit |
electrons (electric charge) |
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how is current related to charge flow? |
curent(a)=charge flow(c)/time(s) charge=current*time time=charge flow/current |
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how are ammeters and voltmeters connected in a circuit |
ammeters in series voltmeters in parallel |
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what is resistance
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a measure of how difficult it is for a charge to flow through a component measured in Ohms resistance+voltage/current |
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how are charge, voltage and energy related? |
voltage=work done/charge |
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what is unusual about a diode? |
only lets current through it in one direction needs about 0.7v before any current flows |
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what are the properties of a thermistor? |
resistance decreases with temperature |
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what are the proporties of ldr |
resistance decreases with ligt |
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what are the properties of a filament lamp |
resistance increases with current/temperature this is because ions in the metal vibrate more at higher tempratures so it is harder for the charge to flow through |
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what are the rules of a series circuit |
current is the same at all points in the circuit volatage is shared across the components |
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what are the rules for parallel circuits |
each loop has the full voltage current is shared across the loops |