physics block revision corrections

viewing angle affects measurement

parallax error

higher thermal conductivity

= higher rate of energy transfer

how does friction act on the motion of an object

friction causes an object to accelerate forwards

elastic deformation

change in size/shape of object that disappears when deforming force is removed

repeat test

reduces effect of random error, find and discard anomalies, take mean

beyond limit of proportionality

break permanently

energy of baby in bouncer

baby bouncer, baby has GPE and spring has EPE which is transferred to baby's KE store

summarise explain questions

padding

increases collision time, rate of change of momentum decreases, force decreases

increase driver's reaction time

= increased thinking distance because d=sxt

braking distance: poor tyre condition/road surface

decrease of friction

road slopes downhill

gravity opposes braking force + resultant braking force is reduced

momentum is conserved

total momentum before = total momentum after

car at max speed

max forward force of motor, air resistance increases as speed increases, forces are equal, car no longer accelerates

increase the moment

apply force further away from the pivot

stopping distance = thinking distance + braking distance

terminal velocity: resultant force is downwards

weight of object vs air resistance

when weight = resistance, resultant force = 0

brick stationary at the bottom of the pool

upthrust acts upwards on the brick, normal contact force acts upwards, weight is greater than upthrust force, weight = upthrust + normal contact force

how does pressure increase with depth (in a fluid)

linearly, p = hpg

why can you reach a faster terminal velocity from greater heights

high altitude = less air molecules = less air resistance, requires much higher speed to match weight, able to accelerate for longer, reaches higher terminal velocity

core prac - V=IR circuits

low current to avoid temp increase, switch circuit off between readings

benefits of digital ammeter

less chance of misleading

prove inverse proportion

two values multiplied = constant, show with 3 pairs of values

electric shock

live wire has a pd of 230V, person is earthed, large pd between earth and person causes current to conduct through person, electric shock

air becomes ionised due to strong electric field

direct pd

polarity does not change

specific latent heat

the amount of energy needed to change the state of 1kg of the substance without changing the temperature

specific heat capacity

the amount of energy needed to increase the temperature of 1kg of a substance by 1˚C

random nature of radioactive decay

cannot predict which nucleus will decay, cannot predict when a particular nucleus will decay

nuclear fission

a uranium nucleus absorbs a neutron, the nucleus splits into two parts and two/three neutrons are released and gamma rays are emitted

nuclear fusion

lighter nuclei join to form heavier nuclei, some of mass of the nuclei is converted to energy of radiation

movement of gas particles

random directions at a range of speeds

electron moving to higher energy level

absorbs energy from EM

electrons moving to lower energy level

electron emits energy in the form of EM radiation

JJ Thompson's Plum Pudding model (1897)

discovered electrons, positively charged mass embedded with small negatively charged electrons

Rutherford's Alpha Particle scattering experiment (1911)

discovered the nucleus (nuclear model), most of the alpha particles passed straight through: atoms are mostly empty space, few deflected then continued path: nucleus has strong positive charge, small number rebounded: small, heavy nucleus

Bohr model (1913)

electrons orbit the nucleus at different distances at different energy levels (2.8.8)

ice to water

as ice was heated, this raised its potential energy as energy used to break bonds, when changing state temp is constant, once water warms particles move faster, KE increases

irradiation

exposure/absorption

contamination

unwanted on/in person

accuracy

closeness to true value

preciseness

measurements are close together

EM spectrum (short to long wavelength)

gamma, xray, ultraviolet, visible, IR, microwaves, radiowaves

earth's gravitational field on satellites

causes to accelerate towards centre, changes direction but not speed, changes velocity

star life cycle (same size as Sun)

protostar, main sequence, red giant, white dwarf, black dwarf

star life cycle (bigger than Sun)

protostar, main sequence, red super giant, supernova, black hole/neutron star

depth of crack

distance x