34 terms

# Poem - Motion, Forces, and Simple Machines

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meter
SI unit of distance, equal to approximately 39.37 inches
m
abbreviation for meter
speed equation
S=d/t
speed units
distance unit divided by a time unit, such as meters per second or m/s
instantaneous speed
speed of an object at any instant of time
speedometer
gives the instantaneous speed when you are riding in a car
average speed
Total distance divided by total time; s=d/t
constant speed
This happens when an object's speed doesn't change for a period of time
distance equation
d=st
velocity
the speed of an object in a particular direction
motion
a state of change
acceleration
the rate at which velocity changes over time
acceleration equation
(final speed - initial speed) / time
gravity
attractive force any two objects that depends on the masses of the objects and the distance between them
Newton's Law
1. an object at rest willl stay at rest, and an object in motion will stay in motion at constant velocity unless acted upon by an unbalanced force 2. force = massXacceleration 3. for every action there is an equal and opposite reaction
force
acted upon an object to change an object's speed, direction, or both
balanced forces
2 or more forces exerted on an object that cancel each other out and don't cause a change in motion
unbalanced forces
2 or more forces that effects don't cancel each other out and cause a change in motion
net force
the combination of all forces acting on an object
Newton's First Law
a moving object moves in a straight line with constant speed unless an unbalanced force acts on it
friction
the force that opposes the motion of one surface as it moves across another surface
how to keep object moving when friction is acting upon it
you have to keep pushing or pulling on the object to overcome the frictional force
In what direction is the force of friction exerted?
opposite direction
size of friction force depends on what?
1. 2 surfaces involved
2. The rougher surfaces are, the greater the friction.
inertia
the tendency of an object to resist a change in motion
heavy object are harder
to move and stop
mass
a measure of how much matter an object is made of.
Newton's Second Law
if an object is acted upon by a net force, the acceleration of the object will be in the in the direction of the net force, and the acceleration equals the net force divided by the mass.
acceleration equation - Newton's 2nd Law
acceleration (in m/s2) = net force (in N) / mass (in kg)
Newton's Third Law
for every action, there is an equal and opposite reaction, or when one object exerts a force on a 2nd object, the 2nd object exerts equal force in the opposite direction on the first object.
action forces
the force you exert when you push on something
reaction forces
are equal and opposite forces exerted in response to applied forces
force equation - Newton's 2nd Law
force=mass x acceleration
why don't action and reaction forces cancel?
action-reaction forces are equal and opposite, but they act on two different objects