Unit B, Chapter 3 &4 Flashcards
(push or pull). a __ is an action capable of acceleration. vector, measured in newtons (N)
Force
tendency of a body to maintain its current state of motion. a property that resists acceleration
Inertia
an object will remain at constant velocity (includes zero) ina straight line unless acted upon by an unbalanced force.AKA law of Inertia
Newton’s first law of motion
The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object. a=F/m
Newton’s second law of motion
- Net force ≠ 0
- Net force = 0
1.unbalanced force
2. balanced force
the vector sum of all forces (total)
Net force
(weight) always downwards
force due to gravity (fg)
(perpendicular to surface) not always opposite to fg
Normal force (fn)
always opposes motion
force of friction (ff)
points away from object in direction on rope
force of tension (ft)
diagram used to represent forces action on a single object. Uses vector arrows. must include: force type,direction, relative motion
Free body diagram (FBD)
Object is stationary. Fx=max=0, Fy=may=0
Statics
Object is accelerating. Fx=max, Fy=may
Dynamics
Every particle in the universe attracts every other particle. This force acts: along a line between 2 particles anf from centre of one object to center of another. Fg=Gm1m2/r2
Newtons law of universal gravitation
sphere of influence. used to explain how forces act at a distance
Field
force per unit mass, vector
gravitational field
always drawn towards the center of an object
field lines for masses
small mass placed in the field of another object & therefore experiences a force
test object
any mass (since all masses produce fields). typically a celestial body
Producing object
g=Gm/r2. the gavitational force per unit mass at a specific location
gravitational field strength
Fg=Gm1m2/r2. force that attracts two objects together.
gravitational force
for every action (force) in nature there is an equal and opposite reaction.
Newton’s third law of motion
mass measurement based on the ratio of known net force on object to the acceleration of object
Inertial mass
force initiated by object A on object B
Action force
force exerted by object B on object A
Reaction force
relates to roughness of contact surfaces.
coefficient of static friction
static friction does not have a fixed magnitude. It varies from 0 to max value, which is reached the instant the object starts to move.
Magnitude of static fritction
always present when two objects are sliding together.
kinetic friction
gravity acts on objects whether or not they are actually touching.
action-at-a-distance force
May be more or less than true weight. Magnitude and direction of acceleration and its direction determines how much extra force is being applied to us.
Apparent weight
On earth the value of Fg acting alone on a mass at rest
true weight
if standing on a stationary surface, the reaction force to Fg that we feel is called __
Weight
