Mechanics Definitions Flashcards
*Displacement
Distance moved in a stated direction (m)
*Scalar
A quantity with magnitude (size) but not direction
*Acceleration
Rate of change of velocity (ms^-2)
*Vector
A quantity with both magnitude (size) and direction
*Velocity
Displacement per unit time (vector) (ms-1)
*One Newton (N)
The force that causes a mass of 1kg to have an acceleration of 1ms-2
*speed
Distance per unit time (scalar) (ms-1)
*instantaneous speed
The speed at a given instant of time. The gradient of displacement-time graph at that instant. (ms-1)
*couple
A pair of equal and parallel but opposite forces, which tends to produce rotation only
*moment of a force
The force multiplied by the perpendicular distance from a stated point (usually the pivot) Nm
*One joule (J)
the work done by a force of one newton when its point of application moves one metre in the direction of the force
*gravitational potential energy (J)
The energy stored in an object by virtue of its position in a gravitational field (and the work that object can do)
Density
Mass per unit volume (kgm-3)
Energy
The stored ability to do work
kinetic energy (J)
The work an object can do by virtue of its speed
Pressure
Force per unit area (Nm-2 or Pa)
Conservation of energy
energy may be converted from one form to another, but cannot be created or destroyed
Power (W)
The rate of doing work
One watt (W)
One joule per second
Terminal velocity
When the net forces on a falling object are zero I.e. The drag equals the weight
Hooke’s law
The extension of an elastic body is proportional to the force that causes it
Equilibrium
When the net force and the net moment on an object are zero
Stopping distance
The sum of the thinking distance and the braking distance
Elastic deformation
Produces a straight line on a tension-extension graph, up to the elastic limit
Principle of moments
When the sum of the clockwise moments equals the sum of the anticlockwise moments
Young’s modulus
The ratio between the stress and strain for a material
Plastic deformation
Produces a curved line on a tension-extension graph, after the elastic limit
Work done
Force x distance, where distance is in the direction of the force
