AS-Level Mechanics OCR G481 Flashcards
define scalar and vector quantities and give examples;
Scalar: Magnitude without direction
Density, volume, temperature etc
Vector: A quantity that has (both) magnitude / size and direction
acceleration, displacement and weight etc
define displacement
Displacement = (net) distance moved in a particular direction.
define instantaneous speed
Instantaneous speed = speed of a body at a specific instance or at a specific point
define average speed
distance travelled / time taken
define velocity
speed in a given direction
define acceleration
Acceleration is the rate of change of velocity (gradient of a velocity vs time graph, change in velocity/time taken)
Define average velocity
(net) displacement / time taken
define the newton;
The (net) force which gives a mass of 1kg an acceleration of 1 ms-2
define the torque of a couple;
**one of forces × perpendicular distance (between forces) **
(Not force x perpendicular distance)
define the moment of force;
moment = force x perpendicular distance from pivot / axis / point
define thinking distance
Thinking distance: The distance travelled (by the car) from when the driver sees a problem and the brakes are applied
Define braking **distance **
The distance travelled (by the car) whilst the brakes are applied and the car stops
define stopping distance
stopping distance: Thinking distance + braking distance. The total distance travelled in the interval between a driver spotting a hazard, and the vehicle coming to a complete stop.
define work done by a force;
work done = force x distance moved in the direction of the force
define the joule;
Energy required to move a weight of 1N (through) a distance of 1 m
define power
The rate at which work is done:
Power = Work done / Time
OR
Power = Energy / Time
Define the Watt
Power required to move 1N through a distance of 1m in 1 sec (Rate of doing work)
Define Stress
force/(cross-sectional) area
Define Strain
extension/original length
Define Young’s modulus
Young modulus = stress/strain / Young modulus is equal to the gradient from stress-strain graph (in the linear region)
Define ultimate tensile strength
Ultimate tensile strength = Maximum stress material can withstand (before fracture)
define the term elastic deformation
Elastic extension (or compression) is proportional to force (as long as elastic limit is not exceeded)
define plastic deformation of a material
Plastic: Material does not return to original length / shape/ size (is permanently deformed / longer) when the force / stress is removed.
Define density
Density = mass/volume or mass per (unit) volume




