motion Flashcards
what is a perfectly elastic collision
a perfectly elastic collision is one where momentum is conserved and kinetic energy is conserved
what is an inelastic collision
kinetic energy isnt conserved but momentum still is
what is impulse
the change in momentum of an object
I = F change in t
units= Ns
newtons first law
an objects state of motion will remain unchanged unless a resultant force acts upon it
newtons second law
the rate of change of momentum of an object is directly proportional to the net force which acts on the object
if mass is constant, this can be written as F= Ma
what is newtons third law a consequence of
newtons third law is a consequence of the conservation of momentum. a net force acting on an object means a change in acceleration which means change in momentum. momentum is always conserved, so whenever one object excerts a force on another, the second object must deliver an equal sized force back onto the first object so that total momentum = 0
what do car safety features do
the increase the time over which change in momentum takes place
what are some car safety features
-crumple zones
-airbags
-seat belts
what is formed when three forces are in equilibrum
a tip to toe triangle
what is wieght
weight is the force experienced by mass due to a gravitational field
what is the centre of mass
the single point that can be considered in which the whole weight acts through
the object will always balance around this point
what makes an object stable
an object with a low centre of mass and a wide base area is most stable
at which point will an object topple over
and object will topple if a vertical line drawn downwards from its centre of mass falls outside of its base area
things to remember about frictional forces
-they always act in the opposite direction to motion
-they convert ek to heat
-they can never speed things up or make something start moving
what does the density of an object depend on
the material of the object
