The flashcards below were created by user
Anonymous
on FreezingBlue Flashcards.
momentum is
a measure of the state of movement of an object dependent on mass and velocity therefore momentum is a vector quantity
momentum formula =
momentum (kg m/s) = Mass (kg) X velocity (m/s)
Force and momentum equation
Force (N) = Change in momentum (kg m/s) / time taken for change(s)
Crumple zones...
increase the time taken for the bodys momentum to reach zero therefore reducing the force
safety technology in cars includes
crumples zones, cushioning during impact(air bags soft seating) and seat belts
Work is done when
a force moves on an object
Work done (J) =
Energy transferred (J)
Work done (full formula) =
Work done (J) = force (N) X distance moved in direction of force (m)
Power =
Work done (J)/time taken(s)
Gravitational potential energy (J)=
Mass (kg) X GFS (N/kg) X vertical height (m)
Kinetic energy (j)=
.5 X Mass(kg) X Velocity2 (m/s2)
The principle of conservation of energy states
energy cannot be created nor destroyed only transferred from one form into another
What is an isotope?
atoms of the same element that have a different number of neutrons
the mass number of an atom =
the number of protons+neutrons
the atomic number of an atom =
the number of protons
an atom is unstable when
its nucleus contains too many or too few neutrons
when unstable nuclei split up they
emit radiation
what are the three main types of radioactive radiation?
Alpha beta and gamma
Alpha is
most ionising least penetrating helium nuclei
Gamma is
Most penetrating least ionising high frequency electromagnetic wave
beta is
a fast moving electron quite ionising and quite penetrative
Nuclear fission is
the process of splitting atomic nuclei
Nuclear fission is a ___ ____
chain reaction (self sustaining series of events)
The products of nuclear fission are
neutrons energy and daughter nuclei ( RADIOACTIVE)
In a PWR control rods are used to
control the rate of fission and therefore the power of the reactor
In a PWR a moderator (water) is used to
slow fast neutrons making them more likely to collide
Nuclear fusion is
the joining together of two or more light atomic nuclei
Nuclear fusion is better because
it produces more energy p/kg or fuel than fission
we cannot use fusion because
nuclei repel - have to be very close together (high pressure) Need to be moving very very fast to over come electrostatic repulsion and close enough to fuse together Temperature/pressure/confinement
Background radiation is
radiation that occurs all around us
the activity of a radioactive isotope is
the average number of disintegrations per second measured in becquerels and decreases over a period of time
the half life of a radioactive isotope is a measurement of the rate of radioactive decay ie the time it takes for half the undecayed nuclei to decay
got it?
ionising radiation can
damage cells and tissues causing cancer including leukaemia or mutations in the cells and can result in the bith of deformed babies in future generations
The uses of radiation include
radiotherapy, gammarays/x-rays, sterilisation of medical instruments, preserving foods, controlling sheet thickness,smoke detectors