Physics Flashcards
1.1 use the following units: kilogram, metre , metre/second, metre/second2, newton , second and newton/kilogram
(kg),(m), (m/s),(m/s2),(N), (s),(N/kg)
1.3 plot and explain distance−time graphs
A distance time graph has distance on the y axis (usually in metres) and time on the x axis (usually in seconds). The gradient of the line (change in y/ change in x) is the speed. If the line is flat then the object is stationary.
1.4 know and use the relationship between average speed, distance moved and time
taken
speed (m/s) = distance travelled (m)/ time taken (s)
1.5 practical: investigate the motion of everyday objects such as toy cars or tennis balls
Apparatus: stop watch and metre rule
mark the start and end positions for the know distance
use a metre rule to measure the distance
line up front of car with start point, release and start timer
move eyes to end point
stop timer when front of car passes end point
improve by repeating and averaging
make sure car starts from stationary
calculate average speed using : average speed = distance travelled/ time taken
1.7 plot and explain velocity-time graphs
on a velocity time graph the velocity-time graph the velocity is on the y axis (usually in m/s) and time is on the x axis (usually in s). If the line is flat then the object is moving at a constant velocity. the gradient of the line is the acceleration. The area under the line is the distance travelled.
1.9 determine the distance travelled from the area between a velocity−time graph and
the time axis
The area under the graph can be calculated as rectangles and triangles, or by counting boxes, is equal to the distance travelled.
1.6 know and use the relationship between acceleration, change in velocity and time
taken:
acceleration =change in velocity/time taken
1.10 use the relationship between final speed, initial speed, acceleration and distance
moved:
(final speed)2= (initial speed)2 + (2 × acceleration × distance moved)
v square= u square + (2 × a × s)
1.8 determine acceleration from the gradient of a velocity−time graph
Acceleration
=rise over run
If the line is horizontal, the velocity is constant (no acceleration).
If the line slopes upwards then the object is accelerating (speeding up).
If the line goes down then the object is decelerating (slowing down).
4.1 use the following units: kilogram joule, metre , metre/second,
metre/second2 , newton , second and watt
(kg), (J), (m),(m/s),(m/s2),(N), (s),(W)
4.2 describe energy transfers involving energy stores:
Chemical – e.g. the food we eat
Kinetic – movement energy
Gravitational – objects that are lifted up
Elastic – e.g. from springs
Thermal – from hot objects
Magnetic – objects in magnetic fields
Electrostatic – charged objectsNuclear – stored within a nucleus
4.4 know and use the relationship between efficiency, useful energy output and total
energy output:
efficiency=useful energy output/total energy output
times by 100%
4.3 use the principle of conservation of energy
In any process energy is never created or destroyed. (It is just transferred from one store to another.)
4.5 describe a variety of everyday and scientific devices and situations, explaining the
transfer of the input energy in terms of the above relationship, including their
representation by Sankey diagrams
The energy flow is shown by arrows whose width is proportional to the amount of energy involved. The wasted and useful energy outputs are shown by different arrows.
4.6 describe how thermal energy transfer may take place by conduction, convection and
radiation
Conduction is the transfer of thermal energy through a substance by the vibration of the atoms within the substance. Metals are good conductors because they have free electrons that can move easily through the metal, making the transfer of energy happen faster.
Convection occurs in a liquid or gas. These expand when heated because the particles move faster and take up more volume – the particles remain the same size but become further apart. The hot liquid or gas is less dense, so it rises into colder areas. The denser, colder liquid or gas falls into the warm areas. In this way, convection currents are set up which transfer heat from place to place.
Thermal radiation is the transfer of energy by infrared (IR) waves. These travel very quickly in straight lines.
4.7 explain the role of convection in everyday phenomena
Convection can be helpful by distributing heat energy, such as in a radiator, to heat the whole room. Hot air rises away from it, creating a current of cool air to be heated.
4.8 explain how emission and absorption of radiation are related to surface and
temperature
– Light, shiny surfaces are good reflectors of IR and so are poor at absorbing it.
– Dark, matt surfaces are poor reflectors and good at absorbing IR.
–This means that placed next to a heat source, a dark object would heat up faster than a light one.
– Dark matt surfaces are also best at emitting IR. This means that a hot object with a light shiny surface will emit less IR than a dark matt object at the same temperature.
–Hotter objects emit more IR per second. The type of EM wave emitted also changes with temperature – the higher the temperature the higher the frequency of EM wave emitted.
4.9 practical: investigate thermal energy transfer by conduction, convection and radiation
Get three beakers and put an insulator around one to stop conduction, a lid on the second to stop convection currents and put nothing on the third as a control.
The beakers must all be the same size and shape and start with the same temp water.
Record how quickly the water in each beaker loses thermal energy
4.10 explain ways of reducing unwanted energy transfer, such as insulation
A good insulating material is a poor conductor that contains trapped air, e.g. foam, feathers, glass fibre. Being a poor conductor (non-metal) prevents heat transfer by conduction and the trapped air prevents convection currents.
4.11 know and use the relationship between work done, force and distance moved in the
direction of the force:
Work done = Force × Distance moved
W = F × d
4.12 know what work done is equal to
energy transferred
4.13 know and use the relationship between gravitational potential energy, mass,
gravitational field strength and height:
Gravitational potential energy = mass × gravitational field strength × height
GPE = m × g × h
4.14 know and use the relationship kinetic energy
Kinetic Energy = 0.5 x Mass x Velocity²
KE= 0.5 × m × v²
4.15 understand how conservation of energy produces a link between gravitational
potential energy, kinetic energy and work
Because energy is conserved the decrease in GPE = increase in KE, for a falling object if no energy is lost to the surroundings
4.16 describe power
Power is the rate of work
Power is also the rate of energy transfer.
So power is how quickly these processes are done.
4.17 use the relationship between power, work done (energy transferred) and time taken:
Power = Work/ Time
P = W/t
5.1 use the following units: degree Celsius, Kelvin, joule , kilogram ,
kilogram/metre3, metre , metre2,metre3, metre/second,metre /second2, newton and pascal (Pa)
(°C), (K), (J),(kg),(kg/m3), (m),(m2), (m3),(m/s), (m/s2), (N) , (Pa)
5.2 use the following unit: joules/kilogram degree Celsius (J/kg °C)
the unit for specific heat capacity: joules/kilogram degree Celsius (J/kg °C)
5.3 know and use the relationship between density, mass and volume:
density= mass/volume
5.4 practical: investigate density using direct measurements of mass and volume
-Measure the mass of the object using an electronic balance.
- Measure the lengths of sides using a ruler or digital calliper, and diameters for sphere or cylinder using a digital calliper. Take several readings at several points for circular objects and work out the average. Use the appropriate equation to work out the volume (e.g. cuboid: 𝑙×𝑤×𝑑, cylinder: 𝜋𝑟2×𝑙)
- Use the equation density = mass/volume to calculate the density
5.5 know and use the relationship between pressure, force and area:
pressure = force/area
5.6 understand how the pressure at a point in a gas or liquid at rest acts equally in all
directions
The pressure at a point in a gas or liquid at rest acts equally in all directions
5.7 know and use the relationship for pressure difference:
pressure difference = height × density × gravitational field strength
p = h × ρ × g
5.15 explain how molecules in a gas have random motion and that they exert a force and
hence a pressure on the walls of a container
Gas laws:
Gas molecules have rapid and random motion.
When they hit the walls of the container, they exert a force.
Pressure = Force/Area
5.16 understand why there is an absolute zero of temperature which is –273 °C
This is the lowest temperature possible, because particles have the smallest kinetic energy that is possible. This happens at 0𝐾=−273℃
5.17 describe the Kelvin scale of temperature and be able to convert between the Kelvin
and Celsius scales
Celsius > Kelvin +273
Kelvin > Celsius -273
5.18 understand why an increase in temperature results in an increase in the average
speed of gas molecules
Temperature is a measure of the average kinetic energy
As you increase the temperature of a gas, the kinetic energy of the gas particles increases and thus their average speed also increases.
5.19 know that the Kelvin temperature of a gas is proportional to the average kinetic
energy of its molecules
The Kelvin temperature of a gas is proportional to the average kinetic energy of its molecules.
5.20 explain, for a fixed amount of gas, the qualitative relationship between:
* pressure and volume at constant temperature
* pressure and Kelvin temperature at constant volume.
When temperature is measured in Kelvin, the pressure of that gas is proportional to the temperature (so long as the volume is kept the same).
If a fixed volume of gas is heated, it’s final pressure, P2, and final temperature, T2, will be related to the original pressure and temperature (P1 and T1) by the equation: P1 / T1 = P2 / T2
5.21 use the relationship between the pressure and Kelvin temperature of a fixed mass of
gas at constant volume:
p1/t1=p2/t2
5.22 use the relationship between the pressure and volume of a fixed mass of gas at
constant temperature:
p1 times v1=p2 times v2
1.11 describe the effects of forces between bodies such as changes in speed, shape or
direction
force can cause an object to:
*speed up
*slow down
*change direction
*change shape
1.12 identify different types of force such as gravitational or electrostatic
weight= downwards force due to gravity
upthrust= upward force on an object on a fluid
friction= resistive force due to 2 objects in contact
air resistance= resistive force due to moving through air
lift= force that uses motion to make an object rise up
reaction force= force acting in the opposite direction
aka drag
tension= force emitted from rope or sting
1.13 understand how vector quantities differ from scalar quantities
scalars are quantities with only magnitude (size)
vectors are quantities with magnitude (size) and direction
1.14 understand that force is a vector quantity
Force has a magnitude measured in (N) but it also has a direction, a push or a pull, up, down, left or right. So force is a vector.
1.15 calculate the resultant force of forces that act along a line
equal forces can mean 2 things=
object is stationary
or it is moving at a constant speed
you know when it would be moving because drag would be acting on it
if more drag is present than thrust then the object is decelerating
1.16 know that friction is a force that opposes motion
Friction is caused by surfaces rubbing. The force always acts in the opposite direction to motion.
1.19 know that the stopping distance of a vehicle is made up of the sum of the thinking
distance and the braking distance
Stopping distance = Thinking distance + Braking distance
rectangle area= thinking time
triangle area= braking distance
reaction time= line between the areas (once they finished thinking and started reacting)
1.20 describe the factors affecting vehicle stopping distance, including speed, mass, road
condition and reaction time
thinking distance is affected by:
focus
alcohol & drugs
speed of the car
braking distance is affected by:
road conditions
tyre conditions
brake conditions
speed of the car
mass of the car
1.22 practical: investigate how extension varies with applied force for helical springs, metal
wires and rubber bands
- set up your apparatus
- measure the length of your spring before hand, without hanging masses
- hang mass of 100 g on the spring
- measure the new length of the spring
- calculate the extensions of the spring
- repeat steps 3-5 changing the mass
- take note of your results table
1.23 know that the initial linear region of a force-extension graph is associated with
Hooke’s law
hooke’s law= extension id directly proportional to force applied. this is shown by the staight lie in the force extension graph. hooke’s law is obeyed as long as the line is straight.
1.24 describe elastic behaviour as the ability of a material to recover its original shape
after the forces causing deformation have been removed
elastic= materials return to their original shape when the forces on them are removed
plastic= materials retain their new shape
2.1 use the following units: ampere , coulomb , joule , ohm , second ,
volt and watt
(A),(C),(J),(Ω),(s),(V),(W)
2.2 understand how the use of insulation, double insulation, earthing, fuses and circuit
breakers protects the device or user in a range of domestic appliances
Fuses Stop the flow of current by melting if the current is too high. So protecting sensitive components and people because if the components function at too higher temperature it can cause a fire.
Circuit breakers again break the circuit if current is too high.
Insulation and double insulation prevent people from touching exposed wires and getting shocks.
Earthing provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.
2.3 understand why a current in a resistor results in the electrical transfer of energy and
an increase in temperature, and how this can be used in a variety of domestic
contexts
- energy is transferred as a result of collisions between electrons flowing in the conductor, and some of this electrical energy is turned into heat
- the heating effect can be utilised in appliances such as heaters, hobs, ovens, toasters and kettles
2.4 know and use the relationship between power, current and voltage:
Power = current x voltage
P = IV
2.5 use the relationship between energy transferred, current, voltage and time:
energy transferred = current x voltage x time
E = I x V x t
2.6 know the difference between mains electricity being alternating current (a.c.) and
direct current (d.c.) being supplied by a cell or battery
AC:
- supplied by the mains
- in an alternating current, the voltage switches direction many times per second and so does the current
- it has a frequency e.g. if its frequency is 50Hz it will have 50 cycles per second and change direction 100 times
DC:
- supplied by a cell or battery
- in a direct current a constant current in one direction is supplied
- conventional current flows from positive to negative
2.7 explain why a series or parallel circuit is more appropriate for particular applications,
including domestic lighting
Series:
- current is spread out over one line
- uses fewer wires, therefore is easier to assemble and uses less power
Parallel:
- each component is connected individually to the circuit
- good for when you want to turn on components individually, e.g. domestic lighting
- if one bulb breaks, the others can still work
2.8 understand how the current in a series circuit depends on the applied voltage and the
number and nature of other components
- the current of a series circuit is the SAME THROUGHOUT
- increasing the voltage increases the current because V = IR (N.B. the sum of all the voltages across the circuit = the voltage from the power source)
- the number of components increases the resistance
- the higher the resistance, the lower the current
2.9 describe how current varies with voltage in wires, resistors, metal filament lamps and
diodes, and how to investigate this experimentally
- resistors, metal filament lamps and diodes all create resistance so any of these will reduce the current
- this can be investigated by setting up a standard test circuit and changing the components and seeing the changing current on the ammeter
2.10 describe the qualitative effect of changing resistance on the current in a circuit
Increasing resistance decreases current
2.11 describe the qualitative variation of resistance of light-dependent resistors (LDRs)
with illumination and thermistors with temperature
LDRs
- at a high light intensity, resistance decreases
- more current can flow through
Thermistors
- at a higher temperature, resistance decreases
- more current can flow through
2.12 know that lamps and LEDs can be used to indicate the presence of a current in a
circuit
know that lamps and LEDs can be used to indicate the presence of a current in a circuit
Lamps and LEDs are used as the light indicates there is a current
2.13 know and use the relationship between voltage, current and resistance:
voltage = current x resistance
V = I x R
2.15 know and use the relationship between charge, current and time:
charge = current x time
Q = It
2.14 know that current is the rate of flow of charge
Current is the rate of the flow of electrons
2.16 know that electric current in solid metallic conductors is a flow of negatively charged
electrons
Electric current in solid metallic conductors is a flow of negatively charged electrons
2.17 understand why current is conserved at a junction in a circuit
- because of the law of conservation of charge, the current must remain the same throughout the circuit
- at a junction, the current splits between all the different paths so they add up to make the same current
I1 = I2 + I3 + I4
2.18 know that the voltage across two components connected in parallel is the same
The voltage of every component in a parallel circuit is the same as the voltage at the power source
2.19 calculate the currents, voltages and resistances of two resistive components
connected in a series circuit
In a series circuit:
- the current is the same at all points in the circuit
- the sum of the voltages across the circuit = the voltage of the power source
- the resistance is the sum of all the individual resistances
2.20 know that:
* voltage is the energy transferred per unit charge passed
* the volt is a joule per coulomb.
voltage is the energy transferred per unit charge passed
- the volt is a joule per coulomb.
- voltage is the energy transferred per unit charge passed
- the volt is a joule per coulomb.
2.21 know and use the relationship between energy transferred, charge and voltage:
energy transferred = charge x voltage
E = Q x V
