Module 3 - Forces/Motion - Defintions Flashcards
(71 cards)
Acceleration
The rate of change of velocity.
Found from the gradient of a velocity-time graph
Archimede’s Principle
The upwards force (upthrust) acting on an object submerged in a fluid is equal to the weight of the fluid it displaces.
Average Speed
Distance over time for the entire region of interest
Braking Distance
The distance travelled between the brakes being applied and the vehicle coming to a stop.
Brittle
A material which shows no plastic deformation before reaching its breaking stress.
Centre of Gravity
The single point through which the object’s weight can be said to act.
Centre of Mass
The single point through which the object’s mass can be said to act.
Compression
The result of two coplanar forces acting into an object. Compression usually results in a reduction in the length of the object.
Compressive Deformation
The changing of an object’s shape due to compressive (pushing or squashing) forces.
Conservation of Energy
In a closed system with no external forces the total energy of the system before an event is equal to the total energy of the system after the event. The energy does not need to be in the same form after the event as it was before the event.
Conservation of Momentum
The total momentum of a system before an event must be equal to the total mometnum of the system after the event, assuming no external forces act. Total momentum is found by the vector addition of the individual momentums of all parts of the system.
Couple
Two equal sized anti-parallel forces that act on an object through different lines of action.
It has the effect of turning without translation (changing the position of the object).
Density
The mass per unit volume of a material.
Displacement
The direct distance between an object’s starting and ending positions.
It is a vector quantity, and so has both a direction and magnitude.
Displacement - Time graphs
Plots showing how displacement changes over a period of time.
The gradient gives the velocity. Curved lines represent an acceleration.
Drag
The frictional force than an object experiences when moving through a fluid.
Ductile
A material is ductile if it can undergo very large amounts of plastic deformation under tension.
Efficiency
The useful output (e.g. power, energy) of a system divided by the total output.
Elastic Collisions
A collision where the total kinetic energy of the system before the collision is equal to the total kinetic energy of the system after the collision.
Elastic Deformation
It a material deforms with elastic behaviour, it will return to its original shape when the deforming forces are removed. The object will not be permanently deformed.
Elastic Hysteresis
A property of polymers such as rubber. This is when the work done to on loading a rubber band is greater than the energy returned when the rubber band is unloaded. This means the loading line sits above the unloading line on a force-extension graph.
Elastic Potential Energy
The energy stored in an object when it is stretched or compressed. It is equal to the work done to stretch/compress the object and can be determined from the area under a force-extension graph.
Equilibrium
For an object to be in equilibrium, the resultant force and the resultant moment acting on the object must be equal to zero.
Extension
The increase in an object’s length