## Glossary of second semester physics

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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 (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