Definitions Flashcards
Vector
A physical quantity that has both magnitude and direction
Eg velocity, force, acceleration, electric current
Scalar
A physical property with a magnitude but not a direction
Eg speed, distance, pressure, potential difference
Displacement
The distance travelled in a particular direction, measured in metres. It is a vector quantity
Instantaneous speed
The speed of an object at a given moment in time
Velocity
The displacement per unit time, measured in metres per second. It is a vector quantity
Acceleration
The rate of change of velocity, measured in metres per second squared. It is a vector quantity
Newton
Unit of force. 1 Newton is the force which gives a mass of 1kg an acceleration of 1ms^-2
What are the 4 factors that affect the magnitude of the drag force?
Velocity, cross-sectional area, roughness of surface, shape
Terminal velocity
The velocity at which an object’s drag equals it’s accelerating force. Therefore there is no resultant force and zero acceleration
Centre of gravity of an object
Is a point where the entire weight of an object appears to act
Couple
A pair of forces that tends to produce rotation only
Torque
The turning effect due to a couple, measured in Newton metres
Moment of force
The turning effect due to a single force, calculate from: force x perpendicular distance from a given point, measured in Newton metres
Thinking distance
The distance travelled from seeing the need to stop to applying the breaks
Braking distance
The distance a vehicle travels while decelerating to a stop
Stopping distance
The sum of the thinking distance and the braking distance
Work done
force x displacement
Joule
Unit of energy. The work done when a force of 1N moves its point of application 1m in the direction of the force
Power
The rate of work done
Watt
Unit of power
1W = 1Js^-1
Stress
Force per unit area, measured in pascals
Strain
The extension per unit length
Young modulus
The ratio between stress and strain, measured in pascals
Ultimate tensile strength
The maximum tensile force that can be applied to an object before it breaks
Elastic deformation
The object will return to its original shape when the deforming force is removed
Plastic deformation
The object will not return to its original shape when the deforming force is removed. It becomes permanently distorted
