Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
41 Cards in this Set
- Front
- Back
|
Describe a sky diver's motion |
o Atfirst there is no drag and so the only force is weight acting downwards o Theresultant force is mg so acceleration downwards o Asit speeds up the drag increases o Eventuallythe drag = the weight and the resultant force becomes zero o Thismeans there is no acceleration o Thebody falls at a constant velocity called terminal velocity |
|
|
The carhas a greater acceleration and uses less fuel than with caravan. Why? |
o The caravan has a larger surface area andweighs more o It has more air resistance o The caravan would need more speed for it tomove and therefore it requires more fuel |
|
|
What isthe principle for moments? |
o The Principle for moments is when the sum ofthe clockwise moments equals the sum of the anticlockwise moments inequilibrium |
|
|
Why do we need seatbelt? |
o Thechange in momentum is the same for the car o The seatbelt increases the time it comes willtake to come to a stop o Thismeans a smaller force will be felt o This means the injuries will be less serious |
|
|
Why doesan object weigh less on the Moon than the Earth? |
o The gravitational field strength is lower o W=mg o So the object ways less |
|
|
Describethe orbit of a comet around the Sun |
o The orbit is elliptical o The comet goes around the Sun o The closer is gets to the sun, the faster itgoes because it gains more kinetic energy |
|
|
Whichplug is safe to use? |
o A light fitting with a plastic cover is safeto use because it is an insulator § This means it won’t let current to flow § The person won’t receive an electric shocko o A earth wire provides the shortest, lowresistance pathway for the shock § The person won’t receive a shock |
|
|
What is the difference between alternating anddirect current? |
o Alternating current is where the current keepschanging direction o Direct current only flows in one direction |
|
|
Explain how an aircraft becomes electricallycharged whilst flying? |
o It rubs against clouds o The electrons transfer from the clouds to theair to the aircraft |
|
|
Dangers of fuelling an aircraft and how toprevent? |
o it could create a spark and the fuel cancause a fire
o connect the plane to the ground so it losesits charge |
|
|
The Clothand Rod |
o the cloth and rod are both insulators o the electrons leave from the cloth to the rodo the rod therefore becomes negatively chargedand the cloth becomes positively charged |
|
|
Thedroplets of the spray have same charge as the sprayer.. An advantage? |
o The droplets have opposite charges to thesprayer o When they leave the droplets repel each otherbecause they have the same charge o This means they spread out evenly as theymove away from each other |
|
|
How does the resistance of an LDR varies as thelight intensity changes? |
o LDR’s are made of semiconductors o As the illumination increases, the electronsare free to move because they gain energy o This means the resistance decreases |
|
|
Whatis an analogue signal? |
o theycontinuously vary o ithas every value of amplitude |
|
|
Whatis a digital signal? |
o Theycan be used on computers o Theyonly have two values: On and Off o Theycan carry more information |
|
|
Whyevaporation leads to cooling? |
o Somesweat particles gain heat energy and move faster o Somesweat particles are fast enough to leave (evaporation) because the hotter thesubstance, the less dense and therefore easier to evaporate o Theremaining average energy decreases o Thebody becomes cooler |
|
|
How is energy transferred from the hot plate to heat up all the potato? |
o Theheat moves from the hot plate to the pan by conduction o Itthen moves through the pan by conductiono Fromthe pan, it moves to the hot water and heats it up by conduction o Thenthe heat moves through the hot water to the potato by convection and conduction |
|
|
How does a microwave work? |
o Thepotato is placed in the microwave has water molecules in it o Theseabsorb the microwaves and become hot by conduction o Thefood cooks by conduction throughout rather than just the inside |
|
|
Why is a sharp knife easier to cut with? |
Ithas a smaller area therefore it creates a larger pressure for the same amountof force |
|
|
How do gases exert a pressure? |
o Gasparticles collide with the walls o Themomentum of the particles changes o Thisexerts a force on the walls o Pressure= force/area o Soa pressure is exerted |
|
|
How does a gas exert a significant pressure? |
o Thereare so many particles o Eachparticle is minuscule but because there are so many of them, we can see aneffect |
|
|
What is the effect of temperature in a gas? |
o Particlesgain more kinetic energy o Whenthe particles collide, they hit with more force because they travel faster orthe change in momentum is greater o Thismeans the pressure is greater o Thereforethe particles hit the wall more frequently so less time is taken as there aremore collisions per second. The rate of momentum is greater, so the force isgreater, therefore the pressure is greater. |
|
|
Comparethe pressures in the coffee at the bottom of full cup and half cup? |
o Pressurein the full cup is greater because P=hrg o Thearea for the cups is the same o Theweight of the liquid is different o Sothe full cup will have a great pressure |
|
|
How would you make a magnet? |
Geta permanent magnet and rub it in one direction against the magnetic material OR Pass a direct currentso all the domains line up in the same direction throughout the sample |
|
|
How do you investigate the magnetic field of a bar magnet? |
o Putthe magnet on a piece of paper and pit a dot on the edge of the magnet at thecorner of the N pole. o Putthe compass on the dot and label the north and south poles o Thenput the compass on the north dot and keep moving it around |
|
|
How to create a uniform magnet? |
o Gettwo magnets and place them with the opposite poles facing each other o Putthem close but make sure they are not touching (the closer they are, the largerthe magnetic field) o Theuniform magnetic field is the center of the poles, not the edges. |
|
|
Howdoes an electric bell work? |
o Whenthe switch is pressed, the current begins to flow through the wire o Thecurrent magnetizes the magnets o Thesoft iron armature gets attracted to the magnets and is pushed by the switch o Thismeans the circuit breaks and the hammer hits the gong o Thenthe magnets de-magnetize and the soft iron armature falls into place o Thenit starts again!! |
|
|
How can you increase the amount of induced voltage? |
o Rotatethe quicker o Usea stronger magnet o Makemore turns on the coil |
|
|
What material are metal rods made from? |
o Theyare made from iron o Itcan easily become magnetized or lose its magnetism |
|
|
Whathappens when a D.C. current is changed to a.c.? |
o Thepolarity of the magnetic field changes o Atmany times a second (50 times if it from mains) o Thereforethe magnetic field doesn’t have time to create repulsion |
|
|
Iodine -131 is used to treat thyroid cancer - why is it suitable for treatment? |
o it has a half-life which is short o it is still ionising o The isotope will go far enough to destroy thetumor but won’t go enough to cause damage. |
|
|
Explain why Beta radiation is more suitable thanalpha and gamma for treatment? |
o Alpha would not do any damage because it isn’tpenetrating enough to damage the tumour o Gamma is too weakly ionising to kill the tumour |
|
|
Why is ashort half-life good for treatment over several weeks? |
o After several weeks the half-life is diminishedbut is still effective enough |
|
|
Describe the method to measure background radiation? |
o Put the sources in a lead container to measure acontrol – so they don’t contribute o Connect your GM tube to a counter (rate meter) o Take three readings of background radiation for 1minute each o Find the average to get a value for thebackground radiation o Do the experiment with a radioactive sourceo Subtract the average background count from thereadings |
|
|
Why didmost of the atoms go straight through the foil? |
o They missed the nucleus which means that there isa lot of space around the nucleus |
|
|
Why did some of the particles deflect in the gold foil experiment? |
o The positive charge on the alpha repelled withthe positive charge in the nucleus |
|
|
Why did only a small proportion of alpha particles deflect at a largeangle? |
o Only a few alpha particles hit the foil head ono Only some were close enough because of a smallpositive charge |
|
|
Why did somealpha particles deflect less than others? |
o The alpha particles may be travelling faster o They were further away from the nucleus |
|
|
Describe how the three daughter neutrons produce a chain reaction? |
o Each of these neutrons hit another (element inquestion’s) nucleus o These split to form more daughter nuclei andneutrons o The process repeats and continues |
|
|
Why is iteasier to hit a nucleus with a neutron? |
o No charge o No electrostatic force o The nucleus and the alpha particle would repel asthey are both positive |
|
|
Describe the process of controlled fission of U-235 in the nuclearreactor |
o Slow moving neutron collides with U-235 nucleus o Produces 2 lighter daughter nuclei, three neutrons and energy o Each ‘new’ neutron is slowed by a moderator whichcan cause fission with another U-235 nucleus o This is called a chain reaction o The control rods determine the rate of energyproduction by absorbing neutrons o The heat energy is transferred to water, whichacts as a coolant. |
