motion, forces and radiation

what is a scalar quantity?

a quantity with magnitude (size) only

what is a vector quantity?

a quantity with both magnitude (size) and direction

is force a vector or scalar quantity

vector

what is displacement

distance an object moves in a straight line

is distance a scalar or a vector?

scalar

is displacement a scalar or vector?

vector

what is velocity

speed in a given direction

is speed a vector or a scalar?

scalar

is velocity a vector or a scalar?

vector

what is the unit of speed/velocity?

metres per second, m/s

what does the gradient of a distance time graph tell us?

the speed

if you have two, straight diagonal lines on a distance time graph, which one shows the greatest speed?

the one with the steepest gradient

how do you calculate a gradient?

divide the change in y by the change in x

what is the approximate speed of a human walking?

1.5 m/s

what is the approximate speed of a human jogging?

3 m/s

what is the approximate speed of a human cycling?

6 m/s

what is the formula for velocity?

v = s/t

what does s stand for in v = s/t?

displacement or distance moved

what is the definition of acceleration?

the rate of change of velocity

how do we work out the rate of change of something?

divide by the time

what changes can cause acceleration?

a change in direction or a change in speed

what is the formula for acceleration?

a = (v-u)/t

what are the units of acceleration?

m/s(squared)

what does the gradient of a velocity time graph tell us?

the acceleration

what does the area under the line of a velocity time graph tell us?

the distance moved

how do you find the distance moved in a velocity time graph?

find the area under the line

what is a subatomic particle?

a particle smaller than an atom

what are the three subatomic particles?

protons, neutrons and electrons

where are protons found in the atom?

in the nucleus

where are neutrons found in the atom?

in the nucleus

where are electrons found in the atom?

in shells around the nucleus

what is between the nucleus and the shells

nothing

what is the relative mass of a proton

1

what is the relative mass of a neutron?

1

what is the relative mass of an electron?

(almost) zero

what is the relative charge of a proton?

1

what is the relative charge of a neutron?

0

what is the relative charge of an electron?

-1

what does the atomic number of an element represent?

the number of protons in that atom

what are nucleons

subatomic particles in the nucleus (neutrons and protons)

what does the atomic mass number of an element represent

the total number of nucleons (protons AND neutrons)

what does the atomic number of an element represent?

the number of protons

what feature of atoms determine which element they are?

the atomic number

how can you work out how many neutrons there are in an atom?

subtract the atomic number from the mass number

what is an ion?

an atom that has lost or gained electrons (and is therefore charged)

what is meant by the term “ionising”

the ability to “knock off” electrons from atoms

what is the centre of an atom called?

the nucleus

where is all of the positive charge in an atom?

in the nucleus

where is most of the mass in an atom?

in the nucleus

what are isotopes

atoms of the same element with a different mass number

isotopes have the same number of?

protons and electrons

isotopes have different numbers of?

neutrons

where does an atom give off radiation from?

the nucleus

what are the three types of radiation from?

alpha, beta and gamma

what is another name for nuclear radiation?

ionising radiation

what is an alpha particle?

a helium nucleus

what subatomic particles are found in an alpha particle?

two protons and two neutrons

what is a beta particle?

a fast moving electron

what is gamma ray?

an electromagnetic wave

when a nucleus have given off radiation what has happened to the nucleus?

it has decayed

what is the minimum needed to stop alpha radiation?

a sheet of paper

what is the minimum needed to stop beta radiation?

a thin sheet of aluminium/metal

what is the minimum needed to stop gamma radiation?

thick layers of lead or concrete

what types of nuclear radiation are deflected (bent) by magnetic fields?

alpha and beta

why can’t gamma radiation be deflected by magnetic fields?

because gamma rays don’t have a charge

order alpha, beta and gamma radiation in order from least to most ionizing?

gamma, beta, alpha

order alpha, beta and gamma radiation in order from shortest range in air to longest range in air

alpha, beta, gamma

what is a use of alpha radiation in the home?

smoke detectors

what is a use of beta radiation?

thickness detecting in paper milling

what are four uses of gamma radiation?

detecting leaks and blockages underground, treatment of cancer, medical tracers, sterilization of medical equipment

which atomic model was accepted before the nuclear model?

the plum-pudding model

who first carried out the alpha scattering experiment?

rutherford

in the rutherofrd alpha scattering experiment what were the alpha particles fired at?

thin gold leaf

in the rutherford alpha scattering experiment, why was the experiment carried out in a vacuum?

to allow the alpha particles to reach the gold leaf

what happened to most of the alpha particles in the rutherford alpha scattering experiement?

passed straight through

what happened to a few alpha particles in the rutherford alpha scattering experiement?

deflected strongly

in the rutherford alpha scattering experiment what was shown by the particles passing straight through?

the atom was mostly empty space

in the rutherford alpha scattering experiment, what was shown by the particles that were strongly deflected?

that the nucleus has most of the mass and a positive charge

what is the definition of the half-life of a radioactive substance

the half-life is the time taken for half of the nuclei to decay

if something has a short half-life does the radiation fade quickly or slowly?

quickly

what does the radioactive contamination of the body mean?

the source of radiation is on/in your body

what does radioactive irradiation mean?

being exposed to radiation without direct contact with the sourcce

what is background radiation?

a low level of ionising radiation that is around us all the time

what are six sources of background radiation?

cosmic rays, radon gas, food, rocks and buildings, medical and nuclear power