physics exam questions Flashcards
why does different refraction happen at a boundary between air and glass?
- different parts of the wavefront enter glass at different times
- and the velocity is less in glass
- so one part of the wave front changes speed before other parts
A student measured degrees of 6.0, 6.3, 6.4 and 5.8 from a 10 degree incidence angle - why should they have NOT recorded these results?
as the resolution of a protractor is 1 degree so it can’t be used to measure to 1dp
Transformer X is used to transform power station electricity into cables for mains electricity in the national grid - why and how does it do this?
It increases the p.d, therefore decreasing the current! this reduces thermal energy transfer (to the surroundings), increasing the efficiency of power transmission
Transformer Y is used to transform mains electricity in the national grid to peoples homes. why and how does it do this?
it decreases the potential difference to a safer value for homes
difference between alpha external and internal radiation?
external - is stopped by skin and low penetrating so not very damaging!!!
internal - absorbed by living tissues, is highly ionising so the contamination can lead to cell mutation and possibly cancer
what type of radiation do tracers use?
gamma
what type of radiation does internal radiotherapy use
Beta
what type of radiation does external radiation use?
high speed x rays
what do control rods do?
absorb the neutrons and slow down the chain reaction
4 cons of nuclear power stations
are very expensive to build, the waste is radioactive and is expensive to store, non renewable so will run out and there is a risk of a nuclear meltdown/explosion
electromagnetic waves are what type of waves?
transverse
sound waves are what type of waves?
longitudinal
what does sound travel fastest through?
solids
what does light travel fastest in (overall and a medium)
vacuum, and air
what is most of the fusion occurring in stars?
Most of the fusion occurring in stars is hydrogen nuclei fusing to become helium nuclei
why does fusion only happen at very high temperatures and pressures?
to overcome the repulsion of the positively charged nuclei
Pros of gas power station vs coal
no sulphuric dioxide released, doesn’t cause acid rain, less carbon dioxide released, less global warming, gas mining is less destructive than coal mining
in nuclear fission how many electrons are released?
2-3
what radiation does nuclear fission release?
gamma rays
in fusion what two lighter nuclei fuse to form what heavier nuclei
2 hydrogen goes to one helium
why does the temperature in a kettle take a while to increase
as the heating element takes time to heat up
if a question asks if two values are inversely proportional how can you explain it?
the two values multiplied by each other will be constant eg nv is 224, 316, etc
at what speed do particles in a gas and liquid move
random speeds
if there is a brick at the bottom of a pool, what forces are acting on it to make it stationary
upthrust acts upwards, while normal contact acts upwards and weight acts downwards and it is equal to the force exerted by two upwards forces leading to a resultant force of 0 and a stationary block!
what is the relationship between the resistance and the length of a wire at a constant temperature
they are directly proportional to each other and so it is a straight line through the origin
what happens when a spring is compressed and how does this help someone jump higher eg on a trampoline
elastic potential energy increases, which is then transferred to the gravitational potential energy store and as the total energy remains constant it allows the gymnast to jump higher
why should an investigation with a spring be done on the floor but table
as it decreases any hazards : a spring on the table may jump and knock over items or spring into someone when mass is removed whereas it’ll be safer on ground
how do you tell if the braking force has decreased
the train will decelerate at a slower rate
what colour is a fuse and what’s the symbol?
brown - it’s a line through a rectangle
At a height of 40km a rocket stops burning fuel but continued upward to a max height of 60km. Explain why velocity decreases between 40 and 60km? USE FRAV
as there is no fuel, the upwards force of thrust decreases, and the weight will also decrease due to the increase in height but not as drastically meaning the rocket decelerates and hence the velocity must decrease
what is an electric field
a region around a charged object where another charged object experienced a force
why does a trolley move faster and easier along a flat floor than a carpet
at there’s less friction between the floor and wheels, so therefore the resultant force increases and the trolley moves faster
what is the relationship between distance from earthquake to seismometer and time between p and S waves arriving?
distance is directly proportional to the time between p and S waves arriving
what is the control variable in the trolley investigation
mass of trolley + mass hanger
how to get max velocity from mean velocity ?
multiply by 2
one similarity of all electromagnetic waves
they are transverse and hence can travel through a vacuum
what are 2 examples of precautions taken to reduce hazard caused by radioactive waste?
buy radioactive waste, store the waste in metal containers
how to work out uncertainty
range/ 2
why does the students hair stand up when they touch the electron ball?
electrons are transferred to the student
her hair is negatively charged
like charges repel, so therefore the electrons on hair repel each other leading to hair standing on end
Determine p.d if thermistor when resistance at 20 degrees is 80 ohms, the V supplied to the circuit is 12V, and the resistance in circuit is 400 ohms
- first determine Overall resistance by adding 80 and 400
- 480 ohms
- work out current from V= IR,substituting in 480 ohms and 12V
- therefore current is 0.025A
- work out p.d from V=IR
- p.d = 2 ohms
why do parachutes allow the passenger module to fall either a lower terminal velocity?
parachutes increase the effective area, so it slows down quicker, so the same air resistance at a lower speed, therefore a resultant force of 0 at a lower speed and hence a lower terminal velocity
