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