second semester physics
Terms
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 position
 location of an object
 distance
 space between two places
 speed
 how fast an object is moving (rate of change of position)
 constant speed
 doesn't change
 average speed
 total distance divided by total time
 instantaneous speed
 at the moment
 velocity
 how fast and what direction object is moving
 average speed formula
 v= d/t
 what is the speed of a truck that travels 15 miles in 20 minutes? (in mph)

v= ?
d= 15 miles
t= 20 minutes
t=20 min x 1hr/60 min = .33 hrs
15 mi/.33 hrs = 45 mph  reference point

frame of reference
"with respect to..."
***usually the earth***  acceleration
 rate of change of velocity
 acceleration formula

a= final velocity  initial velocity

time  from rest a bike accelerates to 12 m/s in 25 s. what is the rate of acceleration?

inital v= 0 m/s
final v= 12 m/s
t= 25 s
a=?
a= 12 m/s  0 m/s

25 s
a= .48 m/s2  unit for acceleration

miles per second squared
m/s2  unit for distance

meters
m  unit for velocity

miles per second
m/s  unit for time

seconds
s  what are the positive and negative accelerations

faster, starting > positve
slower, stopping, turning > negative  inertia
 objects resistance to changes in motion
 force
 push or pull that one object exerts on another
 what can change the velocity of an object?
 force
 balanced forces

cancel each other out
same size
moving in opposite directions
**sum of all forces acting on object = 0 net force  unbalanced forces

net force doesn't equal zero
cause acceleration 
Newton's 1st Law of Motion
"Law of Inertia"  objects at rest stay at rest, objects in motion stay in moving in a straight line at a constant speed unless action on by an unbalanced forced
 gravity

force of attraction between two objects in the universe
depends on mass and distance between them  properties of gravity

bigger the mass, bigger force of gravity
bigger the distance, smaller force of gravity  friction

force that opposes motion
sliding
rolling
fluid (liquid/gas...air resistance)  Newton's 2nd Law of Motion

acceleration of an object increases as the net force on that object increases
force increases, acceleration increases
mass increases, acceleration decreases
(force is proportional to acceleration)  force formula

force= mass x acceleration
f= m x a  unit for force
 kg x m/s2 > NEWTON
 max acceleration of a fist in a karate blow is 3500 m/s2. if the fist has a mass of .70 kg, how much force can the fist exert?

F= ?
m= .70 kg
a= 3500 m/s2
F= .70 kg x 3500 m/s2
F= 2450 N  weight

doesn't equal mass
force of gravity between object and large body (planet)
depends on location
measured w/ scale and Newtons  mass

amount of matter
measured in kilograms
constant everywhere  weight formula

weight= mass x gravity
W= m x g  acceleration due to gravity
 9.8 m/s2
 unit for weight
 Newton
 unit for gravity
 m/s2
 what is the mass of a 400 N rock?

m=?
W= 400 N
g= 9.8 m/s2
400 N= m x 9.8m/s
 
9.8m/s2 9.8m/s2
m= 40.8 kg 
falling objects
(neglect air resistance)  everything falls at same rate of acceleration on earth (9.8 m/s2)

falling objects
(w/ air resistance) 
fluid friction= force that opposes motin
depends on size, shape, speed (more speed, more air resistance)
eventually force of gravity equals air resistance (terminal velocity)  falling objects formula

distance = 1/2 gravity x time squared
d= 1/2gt2 
projectile motion
horizontal throwing  v= d/t

projectile motion
dropping something 
a= final velocity  initial velocity

time
or
d= 1/2gt2  Newton's 3rd Law of Motion

forces always come in pairs (ActionReaction Pair)
when an object exerts a force on another object, then the 2nd object exerts the same size force in the opposite direction on the first object  centripetal force

causes circular motion
always directed towards center of circle  centrifugal force
 no such thing
 centripetal acceleration
 acceleration towards the center of a circular path
 momentum formula

momentum= mass x velocity
p=m x v  law of conversation of momentum
 momentum before a collision is equal to momentum after a collision
 work
 force applied over a distance in the same direction
 work formula
 Work= force x distance
 power
 how fast work is done
 power formula

power= work

time  unit for work
 joule
 unit for power
 watt
 1 hp= ?

550 ftlb

s
and
746 watts  energy
 ability to do work or to create a change in itself or its surroundings
 5 types of energy

mechanical
chemical
electromagnetic
thermal
nuclear  kinetic energy
 energy in form of motion of object
 kinetic energy formula
 KE = 1/2mv2
 potential energy
 energy due to objects position/condition (edge/stretched)
 potential energy formula
 PE= m x g x h
 units for kinetic and potential energy
 joule