Definitons Mechanics Flashcards
displacement
the distance moved by an object in a particular direction.
instantaneous speed
the speed at the precise instant that it is measured (e.g. a car’s speedometer).
average speed
the speed calculated during a period of time.
speed
rate of change of distance
velocity
rate of change of displacement
acceleration
rate of change of velocity
density
mass/volume
torque of a couple
one of the forces x perpendicular distance between the forces
moment of a force
force x perpendicular distance from pivot
work done by a force
force x distance moved in the direction of the force.
power
the rate of work done
force constant of a spring
force per unit extension
scalar
a quantity with magnitude only
vector
a quantity with both magnitude and direction
terminal velocity
the velocity of a falling object when weight = drag.
centre of gravity
a point where the entire weight of an object appears to act.
thinking distance
the distance travelled by the car in the time taken by the driver to react
braking distance
the distance travelled by the car after the brakes are applied until the car stops.
stopping distance
thinking distance + braking distance.
principle of conservation of energy
Energy cannot be created or destroyed; it can only be transferred into other forms.
principle of moments
For an object in equilibrium, the sum of the clockwise moments about a point = the sum of the anticlockwise moments about the same point.
Hooke’s law
extension of a spring is proportional to the force applied (as long as the elastic limit is not exceeded).
stress
Force/Area
strain
Extension/original length
Young modulus
Stress/strain
ultimate tensile strength
the breaking stress of a material
elastic deformation
material returns to original shape when the force is removed.
plastic deformation
material does not return to original shape when the force is removed.
newton
The force which gives a mass of 1{kg} an acceleration of 1 {ms}^{-2}
joule
The work done by a force of 1 {N} moving an object 1 {m} in the direction of the force.
watt
The power transferred by one joule per second
