Chapter 5 and 6: Motion

Terms

copy deck
force
a push or pull
newton
(N) unit of measurement for forces
net force
the combination of all the forces acting on an object
balanced forces
Forces whose net force is 0
unbalanced forces
forces whose net force is not equal to 0 and cause a chage in motion
friction
a force that oppses motion between 2 surfaces that are in contact
Why does friction occur?
Friction occurs b/c no surface is completely smooth. They all have grooves that get caught in those of the other surace when they move past each other, causing friction.
Ways to increase friction
-using an object with more mass, and therefore more weight (more downward force)
-pushing surface w/more force onto other (more downward force)
-make surfaces rougher
Ways to decrease friction
-using an object w/smaller weight
-use smoother surface/smoothen surface
-lubricant
-switch from sliding to rolling friction
What are the types of friction
kinetic friction - friction between moving surfaces
static friction - friction that balances and other forces on the object and keeps it not moving
Gravity
the force of attraction between objects that is due to their masses
types of kinetic friction
-sliding: results from 2 rough surfaces in motion
-rolling: a wheel in contact w/flat surface
-fluid: a gas or liquid opposing motion
Newton's Law of Universal Gravitation
force of attraction btw ll objects depends on madd of objects and distance apart
Forces involved with projectile motion
-Gravity: causes object to accel. downward
-Air resist.: causes horizontal accel to decrease
Explain falling objects
-accelerate due to gravity
-accel. decreases b/c of air resis. but sped keeps increasing but at slower rate until accel=0 and travels at a constant speed until hitting ground
Weight
amount of gravitational force exerted on an object
mass
amount of matter in an object
terminal velocity
the constant velocity of an object in which the force of gravity is equal to the amount of air resis.
free fall
motion of a bosy when only force of gravity is acting on the body
centripetal force
unbalanced force that causes objects to move in a circular path
projectile motion
curved path an object follows when thrown or propelled near the Earth's surface
Newton's 1st law
-objects at rest will stay at rest
-objects in motion will stay in motion until acted on by an unbalanced force
inertia
tendency of an object to resist a change in motion
Newton's 2nd Law
acceleration of an object depends on the mass of the object and amount of force applied
f=ma
Factors Affecting Terminal Velocity
shape
weight
density of air
texture of object
think of skydivers
Newton's 3rd Law
For every action, there is an equal and opposite reaction

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