Physics Paper 1 Revision - A Levels

absolute uncertainties

the interval that a value is said to lie within, with a given level of confidence

accuracy

a measure of how close a measurement is to the true value

analogue apparatus

measuring apparatus such as rulers, beakers and thermometers that rely on the experimenter reading off a scale to determine the measurement

anomalies

data points that don't fit the pattern of the data; you should determine why an anomalous result has occurred before removing it, repeat readings help remove anomalies

control variables

variables that must remain the same throughout an experiment so as to not affect the results

dependent variables

the variable being measured in an experiment; it is dependent on the independent variable; the dependent variable should be plotted on the y-axis of a graph

digital apparatus

measuring apparatus such as ammeters, voltmeters and digital calipers that digitally measure and display a measurement

fiducial marker

a thin marker, such as a splint, that is used to ensure readings are taken from the same place each time; they are used to improve the accuracy of measurements

gradient

the change in the y-axis value over the change in the x-axis value between two points; if the graph is curved, a tangent can be drawn to calculate the gradient at a specific point

independent variables

the variable that is changed by the experimenter in an experiment; the independent variable should be plotted on the x-axis of a graph

line of best fit

a line drawn on a graph to demonstrate the pattern in the plotted data points

percentage uncertainties

the uncertainty of a measurement, expressed as a percentage of the recorded value

acceleration

the rate of change of velocity

average speed

distance over time for the entire region of interest

braking distance

the distance travelled between the brakes being applied and the vehicle coming to a stop; it is affected by the vehicle and road conditions

displacement

the direct distance between an object's starting and ending positions; it is a vector quantity and so has both a direction and a magnitude

displacement-time graphs

plots showing how displacement changes over a period of time; the gradient gives the velocity - curved lines represent an acceleration

free-fall

an object is said to be in free fall when the only force acting on it is the force of gravity

instantaneous speed

the exact speed of an object at a specific given point

projectile motion

the motion of an object that is fired from a point and then upon which only gravity acts; when solving projectile motion problems, it is useful to split the motion into horizontal and vertical components

reaction time

the time taken to process a stimulus and trigger a response to it; it is affected by alcohol, drugs and tiredness

stopping distance

the sum of thinking distance and braking distance for a driven vehicle

thinking distance

the distance travelled in the time it takes for the driver to react; it is affected by alcohol, drugs and tiredness

velocity-time graphs

plots showing how velocity changes over a period of time; the gradient gives acceleration - curved lines represent changing acceleration

velocity

the rate of change of displacement; it is a vector quantity and so has both a direction and a magnitude

Archimedes' Principle

the upwards force acting on an object submerged in a fluid is equal to the weight of the fluid it displaces

centre of gravity

the single point through which the object's weight can be said to act

centre of mass

the single point through which all the mass of an object can be said to act

couple

two equal and opposite parallel forces that act on an object through different lines of action; it has the effect of causing a rotation without translation

density

the mass per unit volume of a material

drag

the frictional force that an object experiences when moving through a fluid

equilibrium

for an object to be equilibrium, both the resultant force and resultant moment acting on the object must be equal to zero

free-body diagram

a diagram showing all the forces acting on an object; it is a good starting point to any mechanics problem

friction

the resistive force produced when there is relative movement between two surfaces

moment of force

the product of a force and the perpendicular distance from the line of action of the force to the pivot

newton

the unit of force

Newton's second law

the sum of the forces acting on an object is equal to the rate of change of momentum of the object; it is also expressed as the net force acting an object equaling the product of the object's mass and acceleration

normal contact force

the reaction force between an object and surface

pressure

the force that a surface experiences per unit area; it is measured in Pascals (Pa)

principle of moments

for an object to be in equilibrium, the sum of the clockwise moments acting about a point must be equal to the sum of the anticlockwise moments acting about the point

tension

the result of two forces acting on an object in opposite, outwards directions

terminal velocity

the maximum velocity of an object that occurs when the resistive and driving forces acting on the object are equal to each other

triangle of forces

a method of determining the resultant force of two forces; the two forces are joined tip to tail and the resultant force is given by the force that would complete the triangle

upthrust

the upwards force that a fluid applies on an object

weight

the product of an object's mass and the gravitational field strength at its location

conservation of energy

in a closed system with no external forces, the total energy of the system before an event is equal to the total energy of the system after the event; the energy does not need to be in the same form after the event as it was before the event

efficiency

the useful output (e.g. power, energy) of a system divided by the total output

gravitational potential energy

the energy gained by an object when it is raised by a height in a gravitational field

kinetic energy

the energy an object has due to its motion; it is the amount of energy that would be transferred from the object when it decelerates to rest

power

the work done or energy transferred by a system divided by the time taken for that to be done

work done

the energy transferred when a force moves an object over a distance

brittle

a brittle object is one that shows very little strain before reaching its breaking stress

compression

the result of two coplanar forces acting into an object; compression usually results in a reduction in the length of the object

compressive deformation

the changing of an object's shape due to compressive forces

ductile

a material is ductile if it can undergo very large extensions without failure; ductile materials can be stretched into wires

elastic deformation

if a material deforms with elastic behaviour, it will return to its original shape when the deforming forces are removed; the object will not be permanently deformed

elastic potential energy

the energy stored in an object when it is stretched; it is equal to the work done to stretch the object and can be determined from the area under a force-extension graph

extension

the increase of an object's length

force-extension graph

a plot showing how an object extends as the force applied increases; for an elastic object, the gradient should be linear up to the limit of proportionality; the gradient gives the spring constant

Hooke's Law

the extension of an elastic object will be directly proportional to the force applied to it up to the object's limit of proportionality

plastic deformation

if a material deforms with plastic behaviour, it will not return to its original shape when the deforming forces are removed; the object will be permanently deformed

polymeric

a material made from polymers

spring constant

the constant of proportionality for the extension of a spring under a force; the higher the spring constant, the greater the force needed to achieve a given extension

strain

the ratio of an object's extension to its original length; it is a ratio of two lengths and so has no unit

stress

the amount of force acting per unit area; its unit is the Pascal (Pa)

tensile deformation

the changing of an object's shape due to tensile forces

ultimate tensile strength

the maximum stress than an object can withstand before fracture occurs

Young's modulus

the ratio of stress to strain for a given material; its unit is the Pascal (Pa)

conservation of momentum

the total momentum of a system before an event must be equal to the total momentum of the system after the event, assuming no external forces act

elastic collisions

a collision in which the total kinetic energy of the system before the collision is equal to the total kinetic energy of the system after the collision

impulse

the change of momentum of an object when a force acts on it; it is equal to the product of the force acting on the object and the length of time over which it acts

inelastic collision

a collision in which the total kinetic energy of the system before the collision is not equal to the kinetic energy of the system after the collision

linear momentum

the product of an object's mass and linear velocity

Newton's First Law

an object will remain in its current state of motion, unless acted on by a resultant force; an object requires a resultant force to be able to accelerate

Newton's Second Law

the sum of the forces acting on an object is equal to the rate of change of momentum of the object

Newton's Third Law

every action has an equal and opposite reaction; if an object exerts a force on another object, then the other object must exert a force back, that is opposite in direction and equal in magnitude

absolute temperature

a temperature value relative to absolute zero

absolute zero

the lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy

avogadro constant

the number of particles that make up one mole of any gas

boltzmann constant

a constant relating the average kinetic energy of the particles in a gas, to the gas' temperature

boyle's law

the pressure of an ideal gas is inversely proportional to its volume when held at constant temperature

brownian motion

the random motion of particles

change of phase

the transitions between solids, liquids and gases; during a change of phase, there is a change of internal energy but not temperature

equation of state of an ideal gas

an equation linking pressure, volume, number of moles, temperature and the ideal gas constant

gas

a phase of matter in which the particles are high energy and free to move; gases will fill the space they are placed in

internal energy

the sum of the randomly distributed kinetic and potential energies of the particles in a given system

kelvin

the unit of absolute temperature

liquid

a phase of matter in which the particles can slide over each other, but still have forces of attraction between each other

solid

a phase of matter in which the particles can only vibrate about fixed positions, due to strong intermolecular forces

specific heat capacity

the amount of energy required to increase the temperature of 1kg of a substance by 1 Kelvin

specific latent heat

the amount of energy required to change the state of 1kg of a substance without a change of temperature

thermal equilibrium

a stable state in which there is no thermal heat transfer between two regions

angular velocity

an object's rate of change of angular position

centripetal acceleration

the acceleration of an object moving in circular motion; any object in circular motion must have an acceleration since the direction of the object, and therefore the velocity of the object, is constantly changing

centripetal force

the resultant force responsible for an object moving in circular motion; centripetal forces always act towards the centre of the object's rotation

frequency

the inverse of time period; the number of rotations per unit time

period

the time taken for one whole rotation

radian

a unit of angle, where 2π equal to one complete angular rotation

angular frequency

a measure of an object's angular displacement per unit time

critical damping

the form of damping that reduces the displacement of an oscillating object to its equilibrium position in the quickest time possible and without further oscillation