G481 Difinitions Flashcards
Vector
A quantity that has magnitude (size) and direction.
Scalar
A quantity that has magnitude (size), but no direction.
Displacement
Distance moved in a particular direction from the starting point.
Instantaneous speed
Rate of change of distance.
Average speed
Total distance/time.
Velocity
Rate of change of displacement.
Acceleration
Rate of change of velocity.
Terminal velocity
Constant velocity reached when an object falls under gravity. The presence of drag forces and resultant force = 0.
Weight
Mass X gravitational field strength.
Centre of mass
The point at which the mass of a body appears to be concentrated (or the point from which the weight of a body appears to act).
Newton
1N is the force that gives 1kg of mass of an acceleration of 1ms-1.
Moment of force
Force X perpendicular distance of force from pivot.
Principle of moments
When a body is in equilibrium, resultant moment = 0 (sum of CW moments = sum of ACW moments about a point).
Couple
Two equal and opposite forces.
Torque of a couple
One of the forces X perpendicular separation of the forces.
Which two conditions are necessary for equilibrium?
- Resultant force = 0 in any direction
2. Resultant moment = 0 about any point
Density
Mass/Volume
Pressure
Force/Area
Thinking distance
Distance travelled between the driver seeing the hazard and applying his brakes.
Braking distance
Distance travelled between the driver applying his brakes and stopping.
Stopping distance
Total distance travelled from seeing the hazard to stopping (or thinking distance plus stopping distance).
Work done
Force X distance moved in the direction of the force
The principle of energy conservation
Energy can not be created or destroyed, just changed from one form into another.
The Joule
1J is the energy enquired to move a weight of 1N (through) a distance of 1m.
Power
Rate of doing work
(or work done/time)
( or energy transferred/time)
The Watt
The power required to move 1N through a distance of 1m in 1s.
Stress
Stress = force/cross-sectional area
Strain
Strain = extension/original length
Young’s modulus
Young modulus = stress/strain
Ultimate tensile strength
Maximum stress a material can withstand (before it breaks)
Elastic deformation
Material returns to original length when the force is removed.
Plastic deformation
Material does not return to original length when the force is removed.
Hooke’s Law
Extension is directly proportional to force (as long as the elastic limit is not exceeded).
