PAPER 1 TOPICS Flashcards
what is a universe
a large collection of billions of galaxies
what is a galaxy
a large collection of billions of stars
what is our solar system in ?
the milky way galaxy
why does gravitational field strength (g) vary?
MASS:
- the larger the mass of the body creating the field, the stronger it’s gravitational field
- the earth is more massive than the moon, so an object would weigh more on earth than it would on the moon
DISTANCE:
- the closer you get to a star or planet, the stronger the gravitational force is.
how does gravitational force cause moons to orbit planets/planets orbit the sun?
- the planets move around the sun in an almost circular orbit (same for the moon around the earth)
- if an object is travelling in a circle it is CONSTANTLY CHANGING DIRECTION (and so CONSTANTLY ACCELERATING), which means there must be a FORCE ACTING ON IT.
- the force causing this is a centripetal force. it acts towards the centre of the circle.
- this force would cause the object to just fall towards whatever it was orbiting, but as the object is already moving, it just causes it to change direction.
- the object keeps accelerating towards what it’s orbiting, but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle.
- the force that makes this happen is provided by the gravitational force. the gravitational attraction of the sun keeps the planets and comets in their orbits around it,
how do artificial satellites orbit the earth?
- satellites are kept in their orbits around planets by the gravitational attraction of the planet.
- some artificial Earth satellites have an orbital period of exactly one day. they’re called GEOSTATIONARY satellites and are useful in communications because they’re always over the same part of the planet
how do comets orbit the sun?
- comets orbit the sun, but have very elliptical orbits with the sun near one end of the orbit
- comets have much longer orbital periods than the earth, as they travel from the outer edges of our solar system.
- a comet travels much faster when it’s nearer the sun than in the more distant parts of its orbit.
- that is because the increased pull of gravity makes it speed up the closer it gets to the sun.
what are the differences in shape of orbits of comets and moons/planets?
- moons/planets = usually slightly elliptical
- comets = very elliptical and elongated
energy stores and transfers units
- kilogram (kg)
- joule (j)
- metre (m)
- metre per second (m/s)
- second (s)
- watt (w)
KINETIC ENERGY STORE
anything moving has energy in it’s kinetic energy store
THERMAL ENERGY STORE
any object- the hotter it is, the more energy it has in this store
CHEMICAL ENERGY STORE
anything that can release energy by a chemical reaction, e.g. food, fuels
GRAVITATIONAL POTENTIAL ENERGY STORE
anything in a gravitational field (i.e. anything that can fall)
ELASTIC POTENTIAL ENERGY STORE
anything stretched, like springs and rubber bands
ELECTROSTATIC ENERGY STORE
e.g. two charges that attract or repel each other
MAGNETIC ENERGY STORE
e.g. two magnets that attract or repel each other
NUCLEAR ENERGY STORE
atomic nuclei release energy from this store in nuclear reactions
MECHANICAL ENERGY TRANSFER
an object moving due to a force acting on it, e.g. pushing, pulling, stretching or squashing
ELECTRICAL ENERGY TRANSFER
a charge moving through a voltage, e.g. charges moving round a circuit
HEATING ENERGY TRANSFER
energy transferred from a hotter object to a colder object, e.g. heating a pan of water on a hob
RADIATION ENERGY TRANSFER
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.
efficiency principle
energy is only useful when it is transferred from one store to a useful store
how do you calculate efficiency?
useful energy output/total energy output x100
- give efficiency as a %
- efficiency can never be equal to or higher than 100%
describe the energy transfers involved in 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 slope (due to friction)
- and then by heating to the thermal energy stores of the surroundings (wasted)
describe the energy transfers involved in a bat hitting a ball
- some energy is usefully transferred mechanically from the kinetic energy store of the bat to the KE store of the ball.
- the rest of the energy is wasted
- some energy in the kinetic energy store of the bat is transferred mechanically to the thermal energy stores of the bat, the ball and their surroundings.
- the remaining energy is wasted by sound
describe the energy transfers involved in 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 store of the heating element and water to the thermal energy store of the surroundings
describe the energy transfers involved in 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
describe the energy transfers involved in 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 the 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.
how can energy be transferred by heating?
- radiation
- conduction
- convection
describe the process of heat energy transfer by RADIATION
- can also be called IR radiation and consists purely of electromagnetic waves.
- all objects are continually emitting and absorbing infrared radiation
- an object thats HOTTER than it’s surroundings emits more radiation than it absorbs (as it cools down)
- and an object thats COOLER than it’s surroundings 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 absorb and emit radiation better than others
describe the process of heat energy transfer by CONDUCTION
- occurs mainly in a solid, where the particles are held tightly together.
- when one particle vibrates, 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 kinetic energy store to the kinetic energy stores 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 stores of the surroundings (or anything else touching the object)
describe an experiment to demonstrate CONDUCTION
- attach beads at regular intervals to one half of a long 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
describe the process of heat energy transfer 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.
