second semester physics
Terms
undefined, object
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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
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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 (Action-Reaction 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 ft-lb
----
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