Download Speed m/s, km/hr, mi/hr Force Newtons (N) Current (I) Amps (A

Physics
1.
2.
Quantity
Units used
Speed
Force
Current (I)
Resistance
Power
Momentum
Energy
Work
Acceleration
m/s, km/hr, mi/hr
Newtons (N)
Amps (A)
Ohms (Ω)
Watts (W)
Kg-m/s
Joules (J)
Joules (J)
m/s2
Change in temperature = ∆T = Final Temperature – Initial Temperature
=Tf - Ti
Change in velocity = ∆V = Vf – Vi
Units
3.
4.
The distance traveled per unit of time.
Spacing or distance covered between equal time intervals
is the same.
0m
1m
2m
3m
4m
|
|
|
|
|
0s
1s
2s
3s
4s
Common units: m/s
and
km/hr
Speed = distance
Time
Instantaneous speed is speed at a given instant. Just look at
speedometer in a car; that is instantaneous speed.
Slope = ∆y = speed
∆x
Steeper slope = faster speed (A)
Shallower slope = slowest speed (C)
Speed
Graphs of constant speed
5.
6.
• A change in speed per unit of time
Acceleration is a change in speed or direction. The distance traveled
during a constant time interval would change.
0m
|
0s
1m
|
1s
3m
|
2s
9m
|
3s
• Unit: m/s2 , or
27m
|
4s
m/s/s
• Acceleration = final speed - initial speed
Change in time
1. Change in direction.
• a = Vf – Vi
∆t
Acceleration Formula
Acceleration
7.
8.
Both graphs show the same motion (acceleration)
Motion under the force of gravitation only
Acceleration due to gravity = 9.8 m/s2
Graphs of Acceleration
Free - Fall
9.
10.
• When the air resistance upward force equals the
downward force of the weight of the object.
• Speed no longer increases but remains constant.
•
Law of Inertia
•
An object in motion remains in motion or an object at
rest remains at rest unless acted on by a net force
(unbalanced force)
Object is at rest or at constant velocity
Forces acting on objects are balanced – no net force
Seatbelts; if no seatbelt car stops and passenger slides
forward
•
•
•
With seat belt.
Without seat belt.
Newton’s
First Law of Motion
Terminal velocity
11.
•
12.
•
Unbalanced forces (net force) cause an object to
accelerate in the direction of the net force.
Net force = mass x acceleration
(Newton’s Second Law)
FNet = m x a
•
Units: kg-m/s2 , or Newton (N)
•
2 kg
Pressure is the force per unit area.
Pressure = force
Units : N/m2 or lbs/in2
area
Less pressure
2
a = 3 m/s
More pressure
FNet = m x a
2 kg x 3 m/s2 = 6 N
Newton’s
Second Law
Weight spread over
large small area.
Pressure
Weight spread over
small area.
14.
13.
•
•
Weight = mass x Acceleration due to gravity
•
W =mxg
•
g = 9.8 m/s2
•
•
For every action there is an equal and opposite
reaction
Forces occur in pairs
Forces act on two different objects
Action: Rocket pushes
gases down.
Reaction: Gases push
rocket up.
= 10 kg x 9.8 m/s2
= 98 kg-m/s2
= 98 N
= 2 kg x 9.8 m/s2
= 19.6 kg-m/s2
= 19.6 N
Newton’s
Third Law
Weight
15.
16.
Work requires that an object must move.
Force must be in the direction of the movement.
Work = Force x distance
Work
Units: N-m , J (joule)
• A machine is used to do work and can:
• Change force and distance or direction
• Uses less force but goes a longer distance
• Cannot take less work with a machine
• Takes more work when friction is present
Machine
17.
18.
Types of pulleys:
Wheel and axle
Levers
Fixed pulley
Screw
Moveable pulley
Block and Tackle
Pulley
•
•
•
Inclined plane
Wedge
Pulley at fixed
height
Changes the
direction of force
Uses the same effort
force as the load
•
•
•
Pulley moves up
and down
Effort force is ½
load force
Load moves ½ as
far as the effort
distance
•
•
IMA = 2
2 load bearing
strands
Pulley
Six Simple Machines
19.
20.
• Three parts: force, load, and fulcrum
• The greater the distance from the load to the
fulcrum the greater the force required.
1st class
2nd class
Wheel and axle or lever attached to a shaft.
Steering wheel
Door knob
Hinge
3rd class
Smaller force on wheel produces larger force on axle.
Levers
Wheel and Axle
21.
22.
Work done is the same no matter what the angle.
The shorter ramp requires more effort
but a shorter distance.
• A screw is a spiral inclined plane.
• An inclined plane wrapped around a cylinder.
• Less force required over a longer distance.
More work is done when friction is present.
Inclined Plane
24.
23.
• Double inclined plane
• When you use a wedge you redirect the force.
While the axe applies force
downward the wedge changes
the force to the sides to split
the log.
Mechanical advantage measures how much the
machine increases your effort force (big MA is better)
Mechanical Advantage = Resistance Force
Effort Force
= Effort Distance
Resistance Distance
MA
= FR = DE
FE
DR
Percent Efficiency = W out
W in
Wedge
x 100 %
Machine
Calculations
25.
26.
•
Rate at which work is done
•
Power = Work
Change in time
p = mxv
P=W
∆t
Time = 2s
Units: kg-m/s,
N-s
Time = 5s
P = W = 10 J = 5 J/s = 5 W
∆t
2s
Units: J/s,
The product of an object’s mass and its velocity.
P= 10 J = 2 J /s = 2W
5s
V = 20 m/s
V = 20 m/s
Watt (W), Kilowatts (KW)
Power
Momentum
27.
28.
The momentum before a collision equals the momentum
after the collision.
Energy = The Ability to do work: Units – Joules (J)
Potential
Kinetic
Mechanical
Energy
Energy
Energy
Stored energy
PE= m x g x h
P before collision = P after collision
Mass x 9.8 m/s2 x height
Energy of motion
KE = ½ mv2
½ x mass x speed2
5Kg (2m/s) + 10 Kg (0m/s) = 5Kg (0m/s) + 10Kg (1m/s)
10 Kg-m
s
+
0 Kg-m
s
=
0 Kg-m
s
10 Kg-m/s = 10 Kg-m/s
Conservation of Momentum
+ 10 Kg-m
s
PE=0J, KE = 30J
KE = 0J, PE = 30
Energy
Sum of PE & KE
29.
30.
Direction of vibration
•
Longitudinal (compression wave)- particles vibrate parallel
to wave direction: Example: Sound
•
Transverse – particles vibrate perpendicular to wave
direction: Example: Light
Medium – material for the wave to travel through
• Mechanical waves – need a medium: Example sound
Electromagnetic waves – do not need a medium Example: Light
• Crest – highest point of a wave
• Trough – lowest point of a wave
a. Wavelength – distance from one crest to another
- Units are in meters (m)
b. Amplitude – distance from the “at rest” position of the
wave to the crest or trough.
Wave Characteristics
Ways to Classify Waves
31.
32.
•
•
•
•
Does not require a medium
Travels at 3.0 x 108 m/s
Vary by frequency and wavelength
Higher frequency has more energy
Gamma | X-ray | Ultra | Visible | Infra | micro | Radio
Rays |
| violet |
| red | waves | waves
• Frequency – Number of vibrations per second
o Units – Hertz (Hz) or 1/s
• Wavelength – Distance from one crest to another
o Units – meters (m)
• Speed = frequency x wavelength
v=fxλ
m/s = 1/s x m
Highest Frequency
Î
Lowest Frequency
Equations for Waves
Electromagnetic Waves
33.
34.
• Result of interference between an incident and a
reflected wave
• Parts of the wave remain stationary (nodes) and
the wave appears not to be traveling.
• Part of the wave that vibrates (antinodes)
A pattern formed by the overlapping of two or more
waves that arrive in a region at the same time.
Constructive
Waves meet and form a larger
wave.
Destructive
Waves meet and form a smaller
wave or cancel out completely.
Interference
Standing Waves
35.
Wave vibrates
in 3 directions.
36.
Wave goes
through filter
Now wave
vibrates in
only one
direction
The bouncing of a wave when it hits a new medium
∠ of incidence = ∠ of refection
Polarizing filter
Sunglasses are polarized to block the glare from shiny surfaces.
Polarization
Reflection
37.
38.
Bending of a wave as it goes from one medium into
another
The bending of a wave around an object or through an
opening.
Less dense to more dense – wave bends toward the normal
More dense to less dense – wave bends away from the normal.
Refraction
Diffraction
39.
40.
An object is forced to vibrate at its natural frequency.
The change in frequency of a wave due to the motion of
the source or of the receiver.
Sound –
In the beginning only
one tuning fork is
vibrating.
Later a second tuning
fork has started to
vibrate.
Light
Red shift – source is moving away
Resonance
Blue shift – source is moving toward
Doppler Effect
(λ moves toward red)
(λ moves toward blue)
41.
42.
Sound Intensity is Measured in Decibels
The intensity of a sound wave
determines its loudness and is
measured in decibels (dB).
When the dB level increases by
10, the actual intensity of the
sound is multiplied by 10. So a
sound that is measured to be 90
decibels (heavy truck) is 10 x
10 = 100 times more intense
than a sound measured to be 70
decibels (busy traffic)
Energy is neither created nor destroyed only converted from one
form to another.
Law of Conservation of Energy
Sound Intensity
43.
44.
•
Energy transfer when two objects are at different
temperatures
•
•
Energy flows naturally from
to
.
Energy transfers until the two objects are at the same
temperature
Heat
Heating Curve of Water
45.
46.
Disposable
Batteries
1. Conduction- transfer by contact (occurs in solids)
vs.
Pollute landfills
Rechargeable
Batteries
More expensive and even more
polluting but last much longer,
so we through away less.
2. Convection – transfer of heat by movement of particles due
to a difference in temperature. (occurs in liquids and gases)
3.Radiation – transfer of heat by electromagnetic waves.
(occurs from the Sun to the Earth)
Solution to disposing batteries is solar cells, but they are
even more expensive.
Problems with Batteries
Three Ways to Transfer Heat
47.
48.
Renewable Resources
Nonrenewable resources
Replaced by natural processes
in a relatively short time.
Examples: Wind, Geothermal,
Solar, Hydroelectric, Biomass
Consumed at rates far faster
than natural processes can
replace them.
Examples: Fossil Fuels, oil,
natural gas, coal
Gives the relationship between
•
•
•
Current (I) – units – amps (A)
Voltage (V) – units – volts (V)
Resistance (R) – units - ohms (Ω)
I
=
V
R
Units:
Current = Voltage
Resistance
Energy Sources
Ohm’s Law
A = V
Ω
49.
Parts of a circuit and symbols:
50.
Series Circuit
•
•
•
•
•
One pathway for electric charges to move
Closed pathway – if one light goes out – all go out
Current is the same in all bulbs I1 = I2 = I3
Voltages add up to equal voltage of the battery
VT = V1 + V2 + V3
Resistances add up RT = R1 + R2 + R3
12 V = 2 V + 6 V + 4 V
6Ω=1Ω +3Ω+2Ω
I = V = 12V = 2 A
R
Parts of a Circuit
51.
Series Circuit
52.
Parallel Circuit
• More than one Pathway –one light goes out and the others stay lit.
• Current is different in each pathway IT = I1 + I2
• Voltage is the same in each parallel branch VT = V1 = V2
• Resistance
RT =
1
=
1
= 2Ω
I1 = V
1 + 1
1 + 1
R
R1
= 12V = 2A
6Ω
1
I2 = V = 12 V = 4 A
R
3Ω
R2
6Ω
6Ω
3Ω
• E = mc2
• E = energy
• m = mass
• c = speed of light = 3 x 108 m/s2
IT = I1 + I2
= 2A + 4 A
= 6A
Parallel Circuit
Einstein’s Equation
53.
54.
Electrical Energy
Electrical Power
• P = IV
• E = Pt
• P = power : unit – Watt (W), (J/s)
• E = energy : unit – Joule (J)
• P = power : unit – watts (W), (J/s)
• I = Current : unit - Amps (A)
•
V = Voltage : units – Volts (V)
• t = time : unit - sec (s)
Electrical Energy
Power of a Circuit