Mechanics Definitions Flashcards
Vector
A quantity with both magnitude and direction.
Scalar
A quantity with only one magnitude.
Displacement
The distance moved by an object in a particular direction (in the direction of the force).
Instantaneous Speed
The speed of an object measured at a particular point in time.
Average Speed
The total distance travelled, by an object, divided by the total time taken.
Velocity
The rate of change of displacement of an object measured in ms-1.
Acceleration
The rate of change of velocity of an object measured in ms-2.
Newton
The force that will give a 1kg mass an acceleration of 1ms-2 in the direction of the force. 1N = 1kgms-2
Torque of a Couple
The product of one of the forces in a couple and the perpendicular distance between them (unit = Nm).
Couple
A pair of equal parallel forces acting in opposite directions on an object.
Moment
The moment of a force about a point is the magnitude of the force multiplied by the perpendicular distance of the point from the line of force (unit = Nm).
Thinking Distance
The distance travelled from the moment the driver sees the need to brake and the point they start braking.
Braking Distance
The distance travelled by an object from applying the brakes until coming to a complete stop.
Stopping Distance
The sum of the braking and thinking distance.
Work Done
Work done = force x distance moved in the direction of force.
Joule
The energy transferred in moving a force of 1N moving through a distance of 1m.
Power
The rate at which work is done. Unit Js-1 or W.
Watt
1J of energy being transferred per second.
Stress
The force acting per unit cross sectional area.
Strain
The deformation produced (extension or compression) per unit length by tensile or compressive forces.
Young’s Modulus
The ratio of stress to strain caused by compressive or tensile forces, provided Hooke’s Law is obeyed.
Ultimate Tensile Strength (breaking stress)
The value of stress at which a material will break.
Elastic Deformation
A material which will return to its original shape and size when deforming forces are removed.
Plastic Deformation
The deformation of a material beyond the material’s elastic limit.
Density
Mass per unit volume.
Pressure
Force per unit contact area.
Conservation of Energy
Energy cannot be created nor destroyed. It can only be transformed from one form to another.
