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Force and Newton's Laws

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force
a push or a pull
net force
the combination of all the forces acting on an object
balanced forces
two or more forces exerted on an object cancel each other out and do not change the object's velocity
unbalanced forces
two or more forces exerted on an object do not cancel each other out so the objects velocity changes
Newton's first law of motion
if the net force on an object is zero, the object at rest stays at rest, while the object in motion stays in motion
friction
the force that brings nearly everything to a stop
Newton's second law of motion
the acceleration of an object equals the net force divided by the mass and is in the direction of the net force
weight
the size of the gravitational force exerted on an object
center of mass
the point in an object that moves as if all the object's mass were concentrated at that point
Newton's third law of motion
forces always act in equal but opposite pairs
static friction
a force that prevents an object from moving
sliding friction
a force that opposes the motion that occurs when one solid surface slides over another
rolling friction
a force that opposes the motion that occurs when an object rolls over a surface
gravity
a force of attraction between objects that is due to their masses
air resistance
a force that opposes the motion of objects that move through the air
acceleration
the rate at which velocity changes
mass
the amount of matter in an object
velocity
the speed and direction of an object
centripetal force
a force that causes an object to move in a circular path
An object will________________ when the net force is zero.
accelerate
_________will never speed up an object.
Friction
the friction that prevents an object from moving when a force is applied is __________ friction
static
The friction that slows down an object that slides is ___________ friction
sliding
A(n)_________helps reduce sliding friction.
wheel
Normal force is supplied by the ________ of the surface
strength
The speed an object reaches when the force of gravity is balanced by the fore of air resistance is called ____________________.
terminal velocity
Earth has so much ____________ that it hardly accelerates when you push against it.
inertia
__________ friction keeps an object a rest.
Static
A force can ____________
either push or pull
The unbalanced force that stops almost anything is _________________
friction`
An object will accelerate in the direction of the _______________
net force
A net force acting on an object changes the object's __________
motion
Newton's__________ law of motion describes the connection between an object supplying force and the object receiving the force.
third
A force in the opposite direction to the motion of the object will cause the object to ____________
slow down
If an object is at rest, all forces acting on that object must be ____________
balanced
Why is it easy to miss an action reaction pair?
It is easy to miss an action reaction pair because one of the objects is often more massive and appears to be motionless
Why does friction never speed up an object?
If 2 objects are in contact, frictional forces always try to prevent one object from sliding on the other.
There is no __________ in time between the action and the reaction
pause
One reason it's often easy to miss an action reaction pair is b/c of the _____________ of one of the objects
size/inertia
Action reaction forces are always the same _________ but are in opposite ___________
force...directions
The ______________ is reached when the force of gravity; the size of the air resistance depends on the shape of an object and its speed
terminal velocity
An object can speed up, slow down or turn in the direction of the net force when the __________ forces act on it.
unbalanced
Galileo realized that an object could be in motion if the ________ acting on it were _____________. In real life, _____________ is the force that ________ _____objects down and causes them to ________. Newton's _________ law of motion described how forces cause the motion of objects to _________: An object at rest remains at rest and an object in motion continues to move in a ___________ line with constant _________if the net force action on it is _____.
force...balance...friction...slows...stop...first...change...straight...speed...zero