4.0 Mechanics And Materials Flashcards
Define terminal velocity
Terminal velocity is the constant velocity that an object reaches when the resistive force acting on it equals the driving force
Define Newtons first law of motion
An object will remain at rest or in constant straight line motion unless acted on by an external force
Define Newtons second law of motion
The rate of change of the velocity is directly proportional to the force acting on it and inversely proportional to the mass
Momentum conservation in transport design
crumple zones, air bags, and seat belts increase the time of impact, resulting in reduced forces on the passengers
Define the elastic limit
The maximum force or extension that a material can withstand while still returning to its original shape when the force is removed
Define elastic strain energy
The energy stored in a material when it is deformed elastically
Define breaking stress
The maximum stress a material can withstand before it fractures or breaks
Define plastic behaviour
It occurs when a material is stretched beyond its elastic limit, causing permanent deformation
How is plastic behaviour shown on a force-extension graph?
Beyond the elastic limit, the graph curves, indicating that the material is undergoing plastic deformation
What is brittle behaviour?
Brittle behaviour occurs when a material fractures with little or no plastic deformation
How is brittle behaviour shown on a force-extension graph?
There is no noticeable curve or plastic deformation before fracture
What happens to energy during deformation within the elastic limit?
When a material deforms within its elastic limit, work is done, this energy is stored as elastic strain energy. The material returns to its original shape when the force is removed, conserving the energy
Define young’s modulus
A measure of a material’s stiffness. The ratio of tensile stress to tensile strain within elastic limit.
