Y11 Separates Physics Keyword List
P2 2 Forces
Word
force
newton (N)
motive force
Definition
gravity
air resistance
A push or a pull.
The unit of force.
Sometimes called the ‘engine force’ or ‘thrust’, it is the force
provided by a machine to make things move.
A resistive force that occurs when two surfaces move over one
another.
A single force that has the same effect as all of the forces acting on an
object.
The force of attraction between any two objects.
A force that acts to slow things down as they move through air.
water resistance
A force that acts to slow things down as they move through water.
velocity
acceleration
The speed of an object in a given direction.
The rate of change in velocity of an object. Acceleration can be due to
a change in speed, or a change in direction.
The quantity of matter in an object.
The force needed to stop a vehicle.
The distance shortest distance a vehicle can stop in. It consists of
both the thinking distance and the braking distance.
The distance travelled by a vehicle in the time it takes for the driver
to react to a situation and apply the brake.
The distance travelled by a vehicle during the time the braking force
acts to stop the vehicle.
The force of gravity upon an object.
The unit of weight.
The force of gravity upon an object per unit mass (the force of gravity
upon a 1 kg mass).
A liquid or gas.
The resistive force that acts upon an object moving through a fluid.
The constant velocity an object reaches when freely falling through a
fluid. The terminal velocity occurs when the size of the objects weight
is exactly balanced by the size of the drag forces upon it.
The property of an object which regains its original shape having
been deformed (e.g. squashed or stretched) by a force.
The increase in length of an object when it is stretched.
There is a directly proportional relationship between two variables
when the second variable increases at a constant rate as the first
increases. On a graph, this would be shown by a straight line through
friction
resultant force
mass
braking force
stopping distance
thinking distance
braking distance
weight
newton
gravitational field
strength
fluid
drag
terminal velocity
elastic
extension
directly
proportional
elastic potential
energy
work done
limit of
proportionality
Hooke’s law
spring constant
speed camera
anti-skid surface
the origin.
The energy stored in an object which has been stretched or
compressed.
The energy transferred by a force.
The limit to which a material can be stretched and still regain its
original shape. Beyond the limit of proportionality the material will be
permanently deformed.
The extension of a spring is directly proportional to the force applied,
provided its limit of proportionality is not exceeded.
The force per unit extension needed to extend a material.
A device used to monitor the speed of vehicles and record the
number plate of any vehicle exceeding the road speed limit.
A rough surface used to increase the friction between tyres and the
road to prevent vehicles skidding in poor weather conditions or at
steep gradients.
P2 3 Work, energy and momentum
Word
work done
gravitational
potential energy
kinetic energy
power
elastic potential
energy
momentum
law of conservation
of momentum
explosion
recoil
impact force
impact time
crumple zone
Definition
The energy transferred by a force.
The energy stored in an object because of its position in a
gravitational field. On Earth, the gravitational potential energy of an
object increases as the object is raised higher above the ground.
The energy of a moving object because of its motion.
The rate of energy transfer.
The energy stored in an object which has been stretched or
compressed.
The mass of an object multiplied by its velocity. It is the tendency of
an object to keep moving in the same direction. An object with more
momentum requires a larger force to stop it in a given amount of
time.
In a closed system, the total momentum before an event is equal to
the total momentum after the event.
An event which is caused by the sudden transfer of stored energy
(such as chemical or elastic potential energy) into kinetic energy.
The movement of a gun backwards when a projectile is fired from it.
Recoil occurs because momentum is conserved in the explosion.
The force between two objects in a collision.
The time over which the impact force is applied.
A region at the front and rear end of a vehicle designed to lessen the
force of an impact.
P3 1 Medical applications of physics
Word
X-rays
radiograph
flat-panel detector
contrast medium
CCD (chargecoupled device)
ionise
computerised
tomography (CT)
scanner
film badge
ultrasound waves
prenatal scan
transducer
partial reflection
A-scan
oscilloscope
transit time
refraction
incident ray
refracted ray
normal
angle of incidence
angle of refraction
refractive index
Snell’s law
critical angle
total internal
reflection
Definition
Electromagnetic waves between ultra violet and gamma rays in the
electromagnetic spectrum. They are commonly used for medical
imaging.
An X-ray picture
A detector used to obtain a radiograph.
A substance which absorbs X-rays easily, which is used to fill soft
tissue organs in order for them to show up on a radiograph.
A device used to obtain an image.
To remove or add electrons to an atom.
A scanner which uses multiple X-ray images to produce a digital
image of any cross-section through the body, or a 3D image of an
organ.
A device worn by people working with ionising radiation which
monitors how much radiation the person is exposed to.
Sound waves with a frequency higher than 20,000 Hz
An ultrasound scan of an unborn foetus.
A device that produces and detects ultrasound waves.
When a wave is partly reflected from a boundary. The rest of the
wave is either absorbed or transmitted through the medium.
An ultrasound scan used to measure the length of an eyeball.
A device used to display the shape of an electrical wave.
The time it takes for an ultrasound wave to pass from the transducer,
to the material boundary, and back to the transducer.
The change in direction of a wave when it passes across a boundary
between two substances (e.g. when light passes from air into glass).
The ray of light acting in towards a boundary.
The ray of light which has been refracted at a boundary.
A line drawn perpendicular (90˚) to a surface.
The angle between the incident ray and the normal.
The angle between the refracted ray and the normal.
A measure of how much a transparent substance refracts light.
The refractive index of a substance is equal to the sine of the angle of
incidence divided by the sine of the angle of refraction.
The size of the angle of incidence when light at a boundary between
a more dense and a less dense substance is refracted so much that it
emerges along the boundary between the two substances.
When all of the light incident at a boundary between a more dense
and a less dense substance is reflected back into the more dense
substance. Total internal reflection occurs if the angle of incidence is
greater than the critical angle.
optical fibre
Very thin glass fibres which are designed to transmit light or infrared
radiation.
endoscope
A device used by doctors to see inside a body cavity without cutting
the body open.
laser
A light source of one pure frequency of electromagnetic waves.
lens
An optical device used to refract light in a particular direction.
converging (convex) A lens which makes parallel rays converge to a single point.
lens
diverging (concave) A lens which makes parallel rays spread out (diverge).
lens
principal focus
The point where parallel rays are focused to by a converging lens, or
the point where parallel rays appear to have come from once they
have passed through a diverging lens.
focal length
The distance between the centre of a lens and its principal focus.
magnification
A measure of the change in size between an image and the original
object.
real image
An image formed where real light rays meet. Real images can be
projected onto a screen.
virtual image
An image, seen in a lens or mirror, from which light rays appear to
come after being refracted by the lens or reflected by the mirror. A
virtual image cannot be projected onto a screen.
principal axis
A straight line that passes along the normal at the centre of each lens
surface.
conjunctiva
The outer surface membrane at the front of the eye.
membrane
cornea
A transparent layer that protects the eye and helps to focus light
onto the retina.
aqueous humour
A transparent watery liquid that supports the front of the eye.
iris
The coloured ring of muscle around the pupil of the eye that controls
the amount of light entering the eye.
pupil
The central hole in the eye which allows light to enter the eye.
eye lens
A transparent convex structure in the eye which focuses light onto
the retina.
ciliary muscles
Muscles which change the thickness of the eye lens.
suspensory
Attach the ciliary muscles to the eye lens.
ligaments
vitreous humour
A transparent jelly-like substance that supports the back of the eye.
retina
The light-sensitive cells around the inside of the eye. The retina
contains two light sensing cells – rods (which detect differences in
light intensity) and cones (which detect colour).
optic nerve
The nerve which carries nerve impulses from the retina to the brain.
blind spot
The region where the optic nerve joins the retina. At this point the
retina has no light-sensitive cells.
fovea
The point on the retina which provides the clearest and sharpest
sclera
near point
far point
range of vision
power of a lens
dioptre (D)
short sightedness
long sightedness
image.
The white of the eye.
The nearest point to an eye at which an object can be seen in focus
by the eye. The near point of a ‘normal’ eye is 25 cm from the eye.
The furthest point from an eye at which an object can be seen in
focus by the eye. The far point of a ‘normal’ eye is at infinity.
Distance from the near point of an eye to its far point.
A measure of how much light is refracted by a lens. A lens with a
higher power has a shorter focal length, and so refracts light by a
larger amount.
The unit of lens power.
The condition when an eye cannot focus on distant objects. The
uncorrected image is focused in front of the retina.
The condition when an eye cannot focus on close objects. The
uncorrected image is focused to a point beyond the retina.
P3 2 Using physics to make things work
Word
moment
lever
effort
load
pivot
fulcrum
line of action of a
force
perpendicular
centre of mass
axis of symmetry
equilibrium
principle of
moments
stability
resultant moment
hydraulics
pressure
pascal (Pa)
Definition
The turning effect of a force.
A simple machine that can increase the size of a force, or increase the
distance the force moves.
The force applied to a lever.
The weight or force upon something.
A point about which something turns.
Another name for a pivot.
The line along which a force acts.
At right angles to (90˚).
The point at which the mass of an object may be thought to be
concentrated.
A line through a shape such that each side is a mirror image of the
other.
The state of an object when it is at rest.
The sum of the clockwise moments must be equal to the sum of the
anticlockwise moments about a point for an object to be in
equilibrium.
How difficult it is to topple an object.
The size of the difference between the sum of the clockwise and
anticlockwise moments about a point.
The use of liquids to perform mechanical tasks.
The force per unit area applied to a surface.
The unit of pressure.
hydraulic pressure
incompressible
hydraulic car jack
centripetal force
centripetal
acceleration
simple pendulum
oscillating motion
amplitude
time period
frequency
The pressure in the liquid in a hydraulic arm.
Cannot be squashed or compressed, so its volume does not change.
A hydraulic device which is used to lift a car.
A resultant force that acts upon an object towards its centre of
circular motion.
The acceleration on a object moving in a circular path. The centripetal
acceleration always acts towards the centre of the circle.
A suspended object that swings freely due to its weight. It consists of
a small spherical bob suspended by a thin string from a fixed point.
Motion of any object that moves to and fro along the same line.
The maximum distance moved by an oscillating object from its
position of equilibrium.
The time taken for an oscillating object to move from its equilibrium
position, to its highest position, back through the equilibrium, to the
next point of highest position and back to the equilibrium such that
one complete oscillation occurs.
The number of oscillations in one second.
P3 3 Using magnetic fields to keep things moving
Word
magnetic compass
magnetic field
north pole
south pole
electromagnet
circuit breaker
relay circuit
motor effect
Fleming’s left hand
rule
electric motor
‘split-ring’
Definition
A small magnetic needle pivoted at its centre.
The region around a magnet where another magnetic material or
magnet experiences a force.
One end of a magnet. It is attracted to a south pole.
One end of a magnet. It is attracted to a north pole.
A coil of wire wrapped around a magnetic metal core (e.g. iron) which
generates a magnetic field when an electric current flows through the
wire.
An electromagnetic switch that opens and cuts the current off if too
much current passes through it.
A low voltage circuit which can be used to control a high voltage
circuit, minimising the electrical risk to the user.
The movement of a current carrying wire when it is placed into a
magnetic field. The motor effect is at its maximum when the wire is
placed perpendicularly to the magnetic field.
A memory aid for learning the direction a current carrying wire will
move when placed in a magnetic field. The thumb, first finger and
second finger of the left hand are held at right angles to each other.
The thumb represents the force (or movement), the first finger
represents the magnetic field direction, and the second finger
represents the direction of conventional current.
A device used to transfer electrical energy to kinetic energy.
Metal contacts on the coil of a direct current motor that connects the
commutator
alternating current
electricity
generator
induce
electromagnetic
induction
National Grid
rotating coil continuously to its electrical power supply.
An electric current which repeatedly reverses its direction.
A device used to transfer kinetic energy into electrical energy.
To cause something to occur without directly interacting with it.
The process of inducing a potential difference in a wire by moving the
wire so it cuts across the lines of force of a magnetic field.
The network of cables and transformers that distributes electricity
from power stations to homes and other buildings.
transformer
An electrical device used to change an alternating voltage.
primary coil
The coil of wire in a transformer that is connected to the power
source.
secondary coil
The coil of wire in a transformer that is connected to the output
circuit.
step-up
An electrical device used to increase an alternating voltage. These are
transformer
used to transfer electrical energy from a power station to the
National Grid.
step-down
An electrical device used to decrease an alternating voltage. These
transformer
are used to transfer electrical energy from the National Grid to
homes and other buildings.
laminated core
The core (often made of iron) in a transformer that is layered to
prevent induced currents inside the core.
switch mode
A transformer that works at much higher frequencies than a
transformer
traditional transformer. It has a ferrite core rather than an iron core.
efficiency
Useful energy transferred by a device divided by the total energy
supplied to the device. It is a measure of how good a device is at
transferring energy usefully.
electrocardiogram A chart which shows how the potential difference generated by the
(ECG)
heart varies with time.
magnetic resonance A scan that uses strong magnetic fields and radio waves to produce
imaging (MRI) scan detailed images of the inside of the body.