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Things You Should Know About Physics
Regents
First Quarter
Fundamental units
Mechanics
Mass (m): = inertia, amount of matter, constant from place
to place, units: kg
Weight (Fg): = force of gravity, changes from place to
place, units: N
Formula:
Quantity
Units
Symbol
Length
meter
m
Mass
kilogram
kg
Time
Electric
current
Temperature
second
s
ampere
A
kelvin
K
Fg = mg
Derived units
Equilibrium: no net force, no acceleration, constant
Quantity
symbol
velocity or at rest, forces form a closed figure.
Velocity
m/s
acceleration
m/s2
N/kg
force
N
Kg m/s
kg m/s
Ns
Work, Heat
Energy
J
Nm
Voltage
V
J/C
eV
1.6x10-19J
N/C
V/m
Frequency
Hz
1/sec
Period
sec
Concurrent vectors:
are added tip to tail.
also
Momentum
Component vectors:
any vector has both X and Y
components. Add components to get resultant.
V2 = Vx2 + Vy2 Angle : = tan-1[Y/x]
Resultant force = Fnet
: head-to-head and tail-to-tail
with components
Equilibrant:
equal and opposite to resultant
&
Impulse
Energy for
subatomic
Electric
Field
Two names for little “g”:
1) acceleration due to gravity, units: m/s2, formula: g = GM/r2
2) gravitational field strength, units: N/kg, formula: g = Fg/m
Scalars (magnitude only)
Distance
Speed
Mass
speed
Anything else!
Vectors (magnitude and direction) – only 9!
Displacement
Velocity
Acceleration
Force (weight, normal force, etc.)
Momentum
Impulse
Fields (gravitational, electric, magnetic)
Kg m2/s2
Things You Should Know About Physics
Vectors
d
Resultant
Concurrent
t
Equilibrant
Maximum 2
Θ = 00
Minimum 2
Θ = 1800
5
Slope = velocity
7
5
3
Triangle rule  sum of any 2 sides ≥ third side
for forces to be in equilibrium
Constant Velocity
Graphs of Motion
v
Two Types of Motion
Constant Acceleration
Forces are balanced
Fnet = 0, a = 0
In equilibrium
Newton’s first law
Forces are unbalanced
Fnet ≠ 0, a ≠ 0
not in equilibrium
Newton’s second law
Distance v. Speed v.
time
time
Distance v. Speed v.
time
time
Acceleration v.
time
Acceleration v.
time
Friction
Static friction (at rest) = applied force until motion starts
Kinetic friction (in motion) is constant
Maximum static friction is greater than kinetic friction
Newton’s Third Law: Whenever A exerts force on B, B exerts equal/opposite
force on A. (Action/reaction pairs: bat and ball, Earth and Moon, hammer and nail)
Forces are the same but the effects of the forces are not:
mA = Ma
t
Slope = acceleration
Area = displacement
Things You Should Know About Physics