A.1 Kinematics - Key terms

kinematics

kinematics

study of motion

classical physics

physics theories that pre-dated the paradigm shifts introduced by quantum physics and relativity

uniform

unchanging

magnitude

size

scalars

quantities that have only magnitude (no direction)

vector

a quantity that has both magnitude and direction

distance

total length travelled, without consideration of directions

displacement, linear

distance in a straight line from a fixed reference point in a specified direction

metre, m

SI unit of length (fundamental)

speed, v

average speed = distance travelled/time taken, instantaneous speed is determined over a very short time interval, during which it is assumed that the speed does not change

reaction time

the time delay between an event occurring and a response, for example, the delay that occurs when using a stopwatch

sensor

an electrical component that responds to a change in a physical property with a corresponding change in an electrical property (usually resistance), also called a transducer

light gate

electronic sensor used to detect motion when an object interrupts a beam of light

second, s

SI unit of time (fundamental)

at rest

stays stationary in the same position

milky way

the galaxy in which our solar system is located

velocity, v

rate of change of position

acceleration, a

rate of change of velocity with time, acceleration is a vector quantity

deceleration

term commonly used to describe a decreasing speed

linear relationship

one which produces a straight line graph

gradient

the rate at which one physical quantity changes in response to changes in another physical quantity, commonly, for an y-x graph, gradient = Δy / Δx

integration

mathematical process used to determine the area under a graph

spreadsheet (computer)

electronic document in which data is arranged in rows and columns of a grid, and can be manipulated and used in calculations

calculus

branch of mathematics which deals with continuous change

differentiate

mathematically determine an equation for a rate of change

equations of motion

equations that can be used to make calculations about objects that are moving with uniform acceleration

air resistance

resistive force opposing the motion of an object through air, a type of drag force

acceleration due to gravity, g

acceleration of a mass falling freely towards earth, on, or near the earth’s surface, g = 9.8 ≈ 10 m/s², also called acceleration of free fall

free fall

motion through the air under the effects of gravity but without air resistance

negligible

too small to be significant

projectile

an object that has been projected through the air and which then moves only under the action of the forces gravity and air resistance

resolve (a vector)

to express a single vector as components (usually two components which are perpendicular to each other)

stroboscope

apparatus used for observing rapid motions, it produces regular flashes of light at an appropriate frequency chosen by the user

trajectory

path followed by a projectile

parabolic

in the shape of a parabola, the trajectory of a projectile is parabolic in a gravitational field if air resistance is negligible

range (of a projectile)

horizontal distance travelled before impact with the ground

impact

collision involving relatively large forces over a short time

imagination

formation of new ideas that are not related to direct sense perception or experimental results

intuition

immediate understanding, without reasoning

inspiration

stimulation (usually to be creative)

drag

force(s) opposing motion through a fluid; sometimes called fluid resistance

fluid

liquid or gas

fluid resistance (friction)

force(s) opposing motion through a fluid; sometimes called drag

terminal speed (velocity)

the greatest downards speed of a falling object that is experiencing resistive forces (for example, air resistance), it occurs when the object’s weight is equal to the sum of resistive forces (+ upthrust)

video analysis

analysis of motion by freeze-frame or slow-motion video replay

thought experiment

an experiment that is carried out in the mind, rather than actually being done, normally because it is otherwise impossible