c04 dynamics II: forces Flashcards
(11 cards)
newtons first law
every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it
balanced forces = 0N
inertia
reluctance of an object to change its state of rest or motion due to its mass
newtons second law
When a resultant force acts on an object of constant mass, the object will accelerate in the direction of the resultant force.
formula for newtons second law
F=ma
newtons third law
If body A exerts a force on body B, then body B will exert an equal and opposite force onto body A. (action-reaction pair)
-Forces always occur in pairs, each pair is made up of an action and reaction force
-Action and reaction forces are equal in magnitude
-Action and reaction forces act in opposite directions
-Action and reaction forces act on different bodies
definition of friction
The contact force that opposes or tends to oppose motion between surfaces in contact
positive and negative effects of friction
positive effects:
We can walk without slipping
Moving objects are able to slow down when needed
negative effects:
Cars are less efficient by up to 20%
Moving parts in engines, motors and machines suffer wear and tear
how to reduce negative effects of friction and enhance positive effects of friction
reducing negative effects of friction:
Using wheels
Using ball bearings
Using lubricants and polishes surfaces
Using air cushion
enhancing positive effects of friction:
Using treads
Using parachutes
Using chalk
objects falling without air resistance
objects can only be in free fall in a vacuum since there is no air resistance
factors affecting air resistance
Increases with the speed of the objects
Increases with the cross-sectional area of the object
Increases with the density of air
what is terminal velocity
When the air resistance against an object equals its weight, the object starts to travel at a constant speed known as terminal velocity, meaning that the object has no acceleration
