U1 definitions Flashcards
Resultant force
sum of all forces
Equilibrium
no resultant force, no moment
Principle of moments
a body will be in equilibrium if the sum of clockwise moments acting on it is equal to the sum of the anticlockwise moments
Gravitational field strength
the force per unit mass
Center of gravity
the point which weight of an object is considered to act
Newton’s first law
an object will remain at rest or in state of uniform motion until acted upon by a resultant force
Newton’s second law
F=ma
Newton’s third law
for every action, there are equal and opposite forces (same type of forces)
Conservation of energy
energy cannot be created or destroyed
Conservation of momentum
In a closed system, sum of momentum before is equal to the sum of momentum after
Hooke’s law
the force needed to extend a spring is proportional to the extension of the spring
Young modulus
stress per unit strain
Elastic deformation
when force is removed, it returns to its original size and shape
Plastic deformation
when force is removed, it cannot return to its original size and shape
Elastic limit
stress beyond which it does not return to its original shape when the force is removed
Limit of proportionality
point beyond which Hooke’s law no longer applies
Yield point
beyond this point, there is little or no increase in stress required to produce large extension
Ultimate tensile stress
highest stress within the material
Tensile stress
stress at which material will break
Breaking stress
material breaks at this point
Hardness
resistance to scratching
Strength
stress needed to break
Strong
requires a large stress to break
Tough
absorb a large amount of energy per volume before fracture
