15: Forces and Matter

Atmosphere

the thin layer of air surrounding the earth, which gets less dense and lowers in pressure with increasing altitude

distortion

the changing of an objects size or shape as a result of a deforming force

elastic distortion

a non-permanent form of distortion for which the object will return to its original shape when the deforming forces are removed

elastic limit

the force beyond which an object will no longer form elastically, and will instead deform plastically

floating

an object will float is the volume of liquid it displaces has a greater weight than that of the object itself. the upthrust acting on the object is greater than its weight

fluid

a liquid or a gas

hooke’s law

the extension of a spring is directly proportional to the force applied to it, up to the limit of proportionality. The constant in this is known as the spring constant

limit of proportionality

the point beyond which the extension of an elastic object is no longer directly proportional to the force applied to it

linear relationship

a relationship between 2 variables where is one variable increases, so does the other by the same factor

plastic distortion

a permanent deformation for which the object will no longer return to its original shape when the deforming forces are removed

pressure in a liquid column =

= height of the column x density of the column x gravitational field strength

sinking

an object will sink if it is more dense than the liquid it displaces. the upthrust acting on the object is lower than its weight and so there is a resultant downwards force

spring constant

a measure of a spring’s stiffness. the higher the spring constant, the smaller the extension is for a given force

upthrust

the upwards force acting on an object in a fluid, due to it experiencing a greater pressure below it than above it. it is equal to the weight of the fluid displaced by the object

weight

the force acting on an object due to gravity

force exerted on a spring =

= string constant x extension

energy transferred in stretching =

= 0.5 x spring constant x extension^2

pressure =

force / area