Physics - Forces

scalar vs vector quantities

scalar - possesses size but no direction

vector - possesses both size and direction

acceleration, velocity, forces

mass

contact vs non-contact

contact - objects are actually touching

friction, air resistance

non-contact - objects are not touching

magnetism, gravity

resultant forces

when one or more forces act upon an object, these forces can be treated as a single force, having the effect of all of them combined

gravity

the force of attraction between all masses. the gravity that affects an object is dependent on its mass and the gravitational field strength that surrounds it

mass - a measure of the amount of matter an object contains

not to be confused with weight, which is the force acting upon an object because of gravity

vector diagrams

vector diagrams are drawn to determine the size and direction (vector) of the overall resultant force (a combination of all active forces)

the forces are represented as arrows, and are drawn connected to each other, from the point of one arrow to the base of another

work done

when a force causes an object to move, work is done on the object

one joule of work is done when a force of one newton causes a displacement of one metre

W = Fs

s - distance (m)

when work is done, energy transfers take place within the system

elasticity - hooke's law

the extension of the spring is directly proportional to the force applied to it

force (N) = spring constant (k) x extension (e)

when an object is stretched and returns to its original form, it has been elastically deformed

if the object does not return to its original form, it has been inelastically deformed. The extension of the object no longer follows hooke's law

there is a limit of proportionality which can be exceeded, in which case the relationship becomes non-linear

the line on a graph will no longer be straight

the spring constant indicates how easy it is to stretch or compress a spring - the higher the constant, the stiffer the spring.

a force that stretches or compresses an object will store elastic potential energy in that object

the amount of work done and the energy stored are equal, provided the spring does not go past the limit of proportionality