Scalars and Vectors
A scalar is a physical property that only has a magnitude and no direction.
A vector is a physical quantity that has both magnitude and direction.
Displacement - the distance travelled in a particular direction, measured in metres
Instantaneous speed - the speed of a object at a given time
Average speed - a measure of the total distance travelled per unit time
Velocity - displacement per unit time
Acceleration - the rate of change of velocity
The centre of gravity/mass is the point where the entire weight of an object appears to act.
A couple is a pair of equal and parellel but opposite forces, which produces a rotation only. The turning effect they produce is called a torque.
The moment of a force is the force x perpendicular distance from the pivot
An object is only in equilibrium if:
- there is no net force acting in any direction
- there is no net turning effect about any point
Thinking distance - the distance travelled between seeing the hazard and applying the brake
Braking distance - the distance travelled between applying the brake and coming to a stop
Stopping distance = braking distance + stopping distance
Work and Conservation of Energy
Work done is force x distance moved in that direction, it can also be considered as energy transferred, measured in joules.
1 joule is the work done when a force of 1N moves its point of application 1m in the direction of the force.
The principle of conservation of energy:
Energy cannot be created or destroyed, only converted from one form to another
Power is the rate at which work is done, measured in watts.
1 watt is equal to 1joule per second
Stress is the force per unit cross-sectional area (Pa)
Strain is the extension per unit length (is a ratio)
Young's Modulus is the ratio between stress and strain (Pa)
Ultimate tensile strength is the maximum tensile force (2 equal and opposite forces) that can be applied to an object before it breaks.
Elastic deformation is where the object will return to its original shape once the deforming force has been removed. Plastic deformation is when the object has become permanently distorted.