Definitions Flashcards
acceleration of free fall (g)
The acceleration of a body falling under gravity. On Earth it has the value of 9.81 m s–2.
acceleration (a)
acceleration (a)
The rate of change of velocity, measured in metres per second squared (m s–2); a vector quantity.
area (A)
A physical quantity representing the size of part of a surface, measured in metres squared (m2).
average speed
A measure of the total distance travelled in a certain time.
braking distance
The distance a vehicle travels while decelerating to a stop.
brittle
A material that distorts very little even when subject to a large stress and does not exhibit any plastic deformation; for example, concrete.
centre of gravity
The point at which the entire weight of an object can be considered to act.
centre of mass
see centre of gravity (N.B although there is a technical difference it is not required at this level).
components of a vector
The results from resolving a single vector into horizontal and vertical parts.
compressive force
Two or more forces that have the effect of reducing the volume of the object on which they are acting.
conservation of energy
Physical law stating energy cannot be created or destroyed, just transformed from one form into another or transferred from one place to another.
couple
Two forces that are equal and opposite to each other but not in the same straight line.
crumple zone
An area of a vehicle designed to increase the distance over which the vehicle decelerates and so reduce the average force acting.
density ()
The mass per unit volume, measured in kilograms per cubic metre (kg m–3); a scalar quantity.
diffraction
When a wave spreads out after passing around an obstacle or through a gap.
displacement (s or x)
The distance travelled in a particular direction, measured in metres (m), e.g. 3 m; a vector quantity.
displacement–time graph
A motion graph showing displacement against time for a given body.
distance (d)
How far one position is from another, measured in metres (m), e.g. 12 m; a scalar quantity.
drag
The resistive force that acts on a body when it moves through a fluid.
drag coefficient
A characteristic that determines the amount of drag that acts on an object.
ductile
Materials that have a large plastic region (therefore they can be drawn into a wire); for example, copper.
efficiency
The ratio of useful output energy to total input energy.
elastic deformation
The object will return to its original shape when the deforming force is removed.
elastic limit
The point at which elastic deformation becomes plastic deformation.
elastic potential energy
The energy stored in a stretched or compressed object (for example a spring), measured in joules (J); a scalar quantity.
energy (E)
The stored ability to do work, measured in joules (J); a scalar quantity.
equations of motion
The equations used to describe displacement, acceleration, initial velocity, final velocity and time when a body undergoes a constant acceleration.
equilibrium
When there is zero resultant force and zero torque acting on an object.
extension (x)
The change in length of an object when a force is applied to it, measured in metres (m).
fluid
A material that can flow from one place to another (i.e. liquids and gases).
force (F)
A push or a pull on an object, measured in newtons (N); a vector quantity.