Paper 1 Fully Assessed topics Flashcards
what does a distance-time graph show?
how far something had travelled.
what does the GRADIENT on a distance-time graph show?
the gradient at any point gives the SPEED of the object.
what do the FLAT SECTIONS on a distance-time graph show?
show where the object has stopped moving.
what does a STEEPER GRADIENT on a distance-time graph show?
means the object is going faster.
what does a CURVE on a distance-time graph show?
curves represent acceleration.
what does a CURVE GETTING STEEPER on a distance-time graph show?
a curve getting steeper means its speeding up. (increasing gradient)
what does a LEVELLING OFF CURVE on a distance-time graph show?
a levelling off curve means its slowing down. (decreasing gradient)
how do you work out the speed from a DISTANCE-TIME graph?
speed of a section = gradient = change in y/change in x
OR for average speed divide total distance travelled by time it takes.
average speed (velocity)
average speed = distance moved / time taken
what is the difference between speed and velocity?
- speed is just how fast you’re going (e.g. 30 mph or 20 m/s) with no regard to the direction
- velocity however must also have the direction specified (e.g. 30 mph north or 20 m/s 060 degrees.)
- this means you can have objects travelling at a constant speed with a changing velocity. this happens when the object is changing direction whilst staying at the same speed.
what is acceleration?
- how quickly velocity is changing.
- this change in velocity can be a change in SPEED or a change in DIRECTION or both.
what is the unit for acceleration?
m/s2
what are the 2 formulas for velocity?
- a = change in velocity / time taken
a = (v-u)/t - 𝑣^2=𝑢^2+2𝑎𝑠
v is final velocity, u is initial velocity, and s is distance travelled when accelerating
what does a velocity-time graph show?
how an object’s velocity changes over time.
what does the GRADIENT on a velocity time graph show?
gradient = ACCELERATION.
what do the FLAT SECTIONS on a velocity time graph show?
flat sections represent STEADY SPEED.
what does the STEEPNESS of a velocity time graph show?
the steeper the graph, the greater the acceleration or deceleration.
what do the UPHILL SECTIONS on a velocity time graph show?
uphill sections (/) are acceleration
what do the DOWNHILL SECTIONS on a velocity time graph show?
downhill sections () are deceleration.
what does the AREA UNDER THE GRAPH on a velocity time graph show?
the area under any part of the graph is equal to the DISTANCE TRAVELLED in that time interval
what does a CURVE on a velocity time graph show?
a curve means CHANGING ACCELERATION
practical: investigating the motion of a toy car on a ramp. METHOD
- set up your apparatus like in this diagram, holding the car still just before the first light gate.
- mark a line on the ramp - this is to make sure the car starts from the same point each time.
- measure the distance between each light gate - you’ll need this to find the car’s average speed.
- let go of the car just before the light gate so that it starts to roll down the slope.
- the light gates should be connected to a computer. when the car passes through each light gate, a beam of light is broken and a time is recorded by data logging software.
- repeat this experiment several times and get an average time it takes for the car to reach each light gate.
- using these times and the distances between light gates you can find the average speed of the car on the ramp and the average speed of the car on the runway.
- using light gates means you don’t get any timing errors as a result of a person reacting slowly.
practical: investigating the motion of a toy car on a ramp. EXPERIMENTING.
- you could try seeing if the mass of the car affects its average speed - just load weights onto it.
- to see how friction affects the motion of the car you could try placing different materials on the ramp. if you do this, make sure they’re laid flat and they don’t change the angle of the ramp in any way.
- you could investigate the acceleration of the car due to gravity by starting it off higher off the ramp and seeing how this affects its average speed.
- you could change the angle of the ramp to see how it affects the speed.
- you could even try with different cars - see how the size, shape and weight of the car affects the speed.
how does friction affect objects?
- if an object has no force propelling it along, it will always slow down and stop because of friction (unless you’re in space).
- friction is a force that OPPOSES MOTION.
- to travel at a steady speed, things always need a driving force to counteract the friction.
in which 3 ways does friction occur?
- friction between solid surfaces which are gripping (static friction)
- friction between solid surfaces which are sliding past each other. you can reduce both these types of friction by putting a lubricant like oil or grease between the surfaces. Friction between solids can ofter cause wear of the two surfaces in contact.
- resistance or “drag” from fluids (e.g. air). the most important factor by far in reducing drag in fluids is keeping the shape of the object streamlined, like sports cars or boat hulls. Lorries and caravans have “deflectors” on them to make them more streamlined and reduce drag. for a given thrust, the higher the drag, the lower the top speed of the car. in a fluid, FRICTION ALWAYS INCREASES AS THE SPEED INCREASES.
what are the 8 energy stores?
energy can be held in different stores:
- MAGNETIC- e.g. 2 magnets that attract or repel each other.
- ELECTROSTATIC- e.g. 2 charges that attract or repel each other.
- NUCLEAR- atomic nuclei release energy from this store in nuclear reactions.
- GRAVITATIONAL POTENTIAL- anything in a gravitational field (i.e. anything that can fall)
- THERMAL- any object, the hotter it is, the more energy it has in this store.
- ELASTIC POTENTIAL- anything stretched, like springs and rubber bands.
- CHEMICAL- anything that can release energy by a chemical reaction e.g. food, fuels.
- KINETIC- anything moving has energy in its kinetic energy store.
how can energy be transferred?
- mechanically- an object moving due to a force acting on it e.g. pushing, pulling, stretching or squashing.
- electrically- a charge moving through a voltage e.g. charges moving round a circuit.
- by heating- energy transferred from a hotter object to a colder object
- by radiation- energy transferred e.g. by light/sound waves, e.g. energy from the Sun reaching earth as light.
what is the principle of conservation of energy?
- energy cannot be created or destroyed, only transferred between stores and dissipated.
- the total energy of a closed system has no net change.
how do energy transfers involve losses?
ENERGY IS ONLY USEFUL WHEN IT IS TRANSFERRED FROM ONE STORE TO A USEFUL STORE.
- useful devices can transfer energy from one store to a useful store.
- however, some of the input energy is always lost or wasted, often to thermal energy stores by HEATING. for example, a motor will transfer energy to its kinetic energy store (useful), but will also transfer energy to the thermal energy stores of the motor and the surroundings (wasted)
- the law of conservation of energy means that:
total energy = useful energy output + wasted energy.
- the less energy thats wasted, the more efficient the device is said to be.
what can you do with wasted energy?
- not much
- the wasted energy thats output by a device is transferred to less useful stores, normally by heating, or by light or sound.
- as the energy is transferred away from the device to its surroundings, the energy often spreads out and becomes less concentrated = it dissipates
- according to the principle of conservation of energy, the total amount of energy stays the same. so the energy is still there, but it cants be easily used or collected back in again.
energy transfers: a ball rolling up a slope
- energy is transferred mechanically from the kinetic energy store of the ball to its GPE store.
- some energy is transferred mechanically to the thermal energy stores of the ball and the slope (due to friction), and then by heating to the thermal energy stores of the surroundings. this energy is wasted.
energy transfers: a bat hitting a ball
- some energy is usefully transferred mechanically from the KE store of the bat, to the KE store of the ball.
- the rest of the energy is wasted.
- some energy in the KE store of the bat is transferred mechanically to the thermal energy stores of the bat, the ball and their surroundings.
- the remaining energy is carried away by sound.
energy transfers: an electric kettle boiling water
- energy is transferred electrically from the mains to the thermal energy store of the kettle’s heating element.
- it is then transferred by heating to the thermal energy store of the water.
- some energy is wasted and transferred by heating from the thermal energy stores of the heating element and the water to the thermal energy stores of the surroundings.
energy transfers: a battery powered toy car
- energy is usefully transferred electrically from the chemical energy store of the battery to the kinetic energy store of the car and carried away by light from the headlights.
- wasteful energy transfers also occur, to thermal energy stores of the car and surroundings, and wastefully carried away by sound.
energy transfers: a Bunsen burner and beaker
- energy is usefully transferred by heating from the chemical energy store of the gas to the thermal energy stores of the beaker and water.
- energy is also wastefully transferred by heating to the thermal energy stores of the stand and surroundings.
- some energy is also carried away by light.
in what 3 ways can energy be transferred by heating?
- conduction
- convection
(both involve the transfer of energy by particles) - thermal radiation occurs in solids, liquids and gases.
how is energy transferred by radiation?
thermal radiation involves EMISSION OF ELECTROMAGNETIC WAVES.
- thermal radiation can also be called IR radiation, and it consists of purely of electromagnetic waves a certain range of frequencies. Its next ti visible light in the electromagnetic spectrum.
- all objects are continually emitting and absorbing IR radiation.
- an object thats hotter than its surroundings EMITS more radiation than it absorbs (as it cools down.)
- an object thats cooler than its surrounding ABSORBS more radiation than it emits (as it warms up)
- you can feel this radiation if you stand near something hot like a fire.
- some colours and surfaces absorb and emit radiation better than others.
how is energy transferred by conduction?
- occurs mainly in solids.
- in a solid, the particles are held tightly together. so when one particle vibrate, it collides with other particles nearby and the vibrations quickly pass from particle to particle.
- THERMAL CONDUCTION IS THE PROCESS WHERE VIBRATING PARTICLES TRANSFER ENERGY FROM THEIR KE STORE TO THE KE STORE OF NEIGHBOURING PARTICLES.
- this process continues throughout the solid and gradually some of the energy is passed all the way through the solid, causing a rise in temperature at the other side of the solid. its then usually transferred to the thermal energy store of the surroundings or anything else touching the object.
describe an experiment to demonstrate conduction.
- attach beads at regular intervals (e.g. every 5cm) to one half of a long (at least 30cm) metal bar using wax.
- hold the metal bar in a clamp stand and, using a Bunsen burner, heat the side of the bar with no beads attached from the very end
- as time goes on, energy is transferred along the bar by conduction and the temperature increases along the rod.
- the wax holding the beads in place will gradually melt and the beads will fall as the temperature increases, starting with the bead closest to the point of heating. this illustrates conduction.
how is energy transferred by convection?
- convection occurs when the more energetic particles move from the hotter region to the cooler region, and transfer energy as they do.
1) Energy is transferred from the heater coils to the thermal
energy store of the water by conduction (particle collisions).
2) The particles near the coils get more energy, so they start moving
around faster. This means there’s more distance between them,
i.e. the water expands and becomes less dense.
3) This reduction in density means that hotter water tends to rise above the denser, cooler water.
4) As the hot water rises it displaces (moves) the colder water out of the way, making it sink towards the heater coils.
5) This cold water is then heated by the coils and rises - and so it goes on. You end up with convection currents going up, round and down, circulating the energy through the water.
describe an experiment to demonstrate convection
- place some purple potassium permanganate crystals in a beaker of cold water. aim to put the crystals to one side of the beaker.
- using a Bunsen burner, gently heat the side of the beaker with the crystals at the bottom
- as the temperature of the water around the potassium permanganate crystals increases, they begin to dissolve, forming a bright purple solution.
- this purple solution is carried through the water by convection, and so traces out the path of the convection currents in the beaker.
how can you reduce the rate of energy transfer?
- materials with a high thermal conductivity transfer energy between particles quickly.
- to reduce energy transfers from a system by conduction, use materials with low thermal conductivity.
- to reduce convection, you need to stop the fluid moving, and prevent convection currents from forming.
- insulation uses both of these techniques to reduce energy transfers.
- insulation such as clothes, blankets and foam cavity wall insulation all work by trapping pockets of air. The air can’t move so the energy has to conduct very slowly through the pockets of air, as well as the material in between, both of which have a low thermal conductivity.
- some colours and surfaces will absorb and emit IR radiation better than others.
- so to reduce the energy transfers away from an object by thermal radiation, the object should be designed with a surface that is a poor emitter.
what surfaces are best for absorbing and emitting radiation?
- a black surface is better at absorbing and emitting radiation than a white one
- a matt (dull) surface is better at absorbing and emitting radiation than a shiny one.
what is wavelength?
the distance from peak to peak
what is frequency?
how many complete waves there are per second (passing a certain point). measured in Hertz. 1Hz is 1 wave per second.
what is amplitude?
the height of the wave (from rest to crest)
what is wave speed?
how fast the wave goes
what is the time period?
the time taken (s) for one complete wave to pass a point.
f= 1/t
wave speed =
frequency x wavelength
what is a transverse wave?
most waves are transverse:
- light and all other EM waves
- a slinky spring wiggled up and down
- waves on strings
- ripples on water.
in TRANSVERSE WAVES THE VIBRATIONS ARE AT 90 DEGREES TO THE DIRECTION ENERGY IS TRANSFERRED BY THE WAVE.
what is a longitudinal wave?
some longitudinal waves are:
- sound and ultrasound
- shock waves e.g. some seismic waves
- a slinky spring when you push the end
in LONGITUDINAL WAVES THE VIBRATIONS ARE PARALLEL AS THE WAVE TRANSFERS ENERGY.
what do all waves do?
- all waves transfer energy and information without transferring matter.
- all waves carry and transfer energy in the direction they’re travelling. E.g. microwaves in an oven make things warm up, their energy is transferred to the food you’re cooking. sound waves can make things vibrate or move, e.g. loud bangs can start avalanches.
