Forces & Motion Flashcards
what is newtons third law
when two objects interact with each other, they exert EQUAL AND OPPOSITE forces on each other - the famous phrase EQUAL AND OPPOSITE has 3 words, so this is Newton’s THIRD law.
what is a scalar quantity?
a quantity with only magnitude
what is a vector quantity?
a quantity with magnitude AND direction
what do the length of the arrow symbolise in force diagrams
the magnitude of the force and the direction of the force
unit of forces?
Newtons(N)
what are contact forces
when two objects must be in contact to interact
examples of contact forces
friction, air resitance, tension
examples of vector
velocity, displacement, acceleration, force, momentum, and weight
examples of scalar
speed, mass, distance, time energy, power
what is resultant force
the overall force on an object
newtons first law?
the forces acting on an object are balanced if the resultant force on the object is 0
what is moment
the turning effect of a force
equation of moment
force x distance( perpendicular distance from the line of action of pivot)
unit of moments
newton meters
how to remember moment
moment = time = clock = round= turning force
principle of moments
sum of all clockwise moments about a point = sum of all anit-clockwise moments about that point
what is momentum
momentum is mass times velocity
velocity is?
speed with a given distance
what is conservation of momentum
conservation of momentum = TOTAL momentum before = TOTAL momental after
equation linking force and momentum
force equals change in momentum/ time
explain how:
1. foam on a poll reduces the force of a motorcycle crash
2. a crumple zone reduces the effect on the people inside a car crash
force and time are indirectly portional,
these things increase the time of the impact, by increasing the time of the impact they are reducing the rate of change of momentum and so reducing the force
