Download Motion and light2012

Motion and Light
Mav Mark
If Speed = Distance/time, What
is the speed of a car
That travels 120 miles in 2
hours?
Mav Mark
Draw a distance/time graph and plot the following
information.
A car takes 1 minute to travel 100km. It stops for thirty
seconds, Then continues on for 1 minute as it goes
another 1km.
Mav Mark
What is the difference between the
lithosphere and the asthenosphere?
Mav Mark
1. What forms at an Oceanic-Continental Convergent boundary?
2. What forms at a Continental-Continental Convergent boundary?
Mav Mark
1. What forms at an Oceanic-Oceanic
Convergent boundary?
2. What forms at an Oceanic-Oceanic
Divergent boundary?
3. What forms at a ContinentalContinental Divergent boundary?
Mav Mark
How can you tell the difference
between distance/time graphs
and Speed/time graphs?
Mav Marks
1. Draw a force diagram that shows
balanced forces acting on an object.
2. Draw a force diagram showing
unbalanced forces acting on an object,
and tell which direction the object will
move.
Mav Mark
Write Newton’s three laws of motion
and give an example that
demonstrates Each.
Mav Mark
1. Draw and label the
Electromagnetic Spectrum.
2. Draw and label a transverse
mechanical wave.
Mav Mark
Test Day
Take out a Pencil and a Sheet of
Paper
Clear your Desk
Motion



Motion is a change in position over time.
Motion depends on a reference point which is
an object used for comparison with the object
in motion. Stationary objects are good
reference points.
Position is an object’s location in relation to a
reference point.
Reporting Motion

Qualitative: Describing motion


Fast or slow
Quantitative: measuring motion



Speed = Distance
Time
Speed = 120 miles
2 hours
Speed = 60 miles/hour
Speed vs Velocity

Velocity is speed plus direction.




Speed = 60 miles/hour
Velocity = 60 miles/hour north
Distance is how far the object traveled.
Time measures how long it took the object to
travel the distance.
SPEED
Speed is the distance that an object travels in a period of time.
Units are meters and seconds
However, sometimes km/hr is
more sensible.
d
t
v
A cyclist travels 25 km in ½ an hour.
What is their speed
- in kmhr-1
= 25km/0.5hr
= 50km/hr
- in ms-1
= 25000m/1800s
= 13m/s
DISTANCE/TIME GRAPHS
A car takes 1.5 minutes to travel 500m down a busy road. It stops
at lights for 30 seconds, then continues on for 1 minute as it goes
another 1km.
Plot this on a distance/time graph.
Using the distance/time
graph:
1.5
Distance
1
Δd =
1km
(km)
1.What is the total distance
0.5
traveled?
= 1.5 km
2. In what part of the trip is
= part 3
the car going the fastest?
3. What is the fastest
speed?
v = Δd / Δt
v = 1km/1min
v = 1000m/60s
v = 16m/s
Steepest
section is
fastest
Δt =
1min
1
2
Time (min)
3
In a distance/time graph
the slope of the line =
the speed of the object.
SPEED QUESTIONS
What would these look like on a distance/time graph?
1. stopped
2. slow
3. fast
4. accelerating
Motion on Earth




Theory of Plate Tectonics states that Earth’s
plates move slowly in various directions through
convection energy transfer in the mantle. (some
push away; some push together)
Tectonic plates are large pieces of the
lithosphere that are in constant motion.
Some move cm each year; others just mm
Distance=5cm/year x 1000 years=5000cm (50m)
Motion on Earth

Lithosphere is the rocky outer shell of Earth that
includes the crust and upper mantle. (brittle and
rigid) more solid



Continental Crust: composed of sedimentary, igenous,
and metamorphic rocks and make up the continents
Oceanic Crust: more dense, thinner mafic rock layer
that makes up ocean basins
The asthenosphere lies just below the
lithosphere. It is much hotter with a low density
and very ductile. (plastic and flowing) more liquid
Motion on Earth




Plate Boundary: Region where two tectonic
plates meet
Transform (fault) boundary: Plates slide side
by side.
Convergent boundary: Plates move towards
each other.
Divergent boundary: Plates move away from
each other.
Oceanic-Continental Convergent: Oceanic
plate is more dense and subducts the continental
plate creating an ocean trench and a chain of
volcanoes.
Continental-Continental Convergent: The
two plates collide creating a mountain range.
Oceanic-Oceanic Convergent: collide to
create volcanoes and islands in between.
Oceanic-Oceanic Divergent: Forms midoceanic ridges leading to underwater volcanoes
that give rise to volcanic islands.
Continental-Continental Divergent:
Produce rift valleys eventually creating oceanic
plates.
Motion on Earth
Acceleration



Acceleration is the rate of change in speed,
direction, or both.
Riding your bike at 2 km/h, you slow down to
1 km/h, and then increase speed to 1.5 km/h.
(Each time you are accelerating)
acceleration = velocity final - velocityinitial
time
ACCELERATION
Acceleration is the change in speed in an object in a period of
time.
Δv
Units ms2
Δt
a
It takes a cyclist 20 seconds to go from
a standing start to 14m/s.
What is their acceleration?
a = Δv/Δt a = 14m/s / 20s
What is 14m/s in km/hr?
= 14 × 60s × 60min  1000m
a = 0.7ms2
= 50.4km/hr
SPEED/TIME GRAPHS
A runner travels at 4m/s for 10 seconds, then stops suddenly for 5
seconds, then accelerates for 5 seconds to get to 8m/s and
continues for 10 seconds.
Plot this on a speed/time graph.
Using the speed/time
graph:
In what part of the trip
is the runner going the
fastest?
= part 5
What is the
acceleration in part 4?
a = Δv/Δt
a = 8m/s/5s
a = 1.6ms-2
Speed
8
(m/s)
4
10
20
Time (sec)
In a speed/time graph the
slope of the line = the
acceleration of the object.
30
ACCELERATION QUESTIONS
What would these look like on a speed/time graph?
1. stopped
2. slow
3. fast
4. accelerating
SPEED/TIME GRAPHS
In a speed/time graph the distance covered = the area under the graph.
Part Part
2
3
What distance is covered in part 1?
Speed
d=v×t
8
(m/s)
d = 4m/s × 10s
4
d = 40 m
What is the total distance covered?
Part 1 = 40m
Part
4
Part
1
10
Part 2 = 0m
Part 3 = v × t × 
= 8m/s × 5s × 
= 20m
Part 4 = v × t
= 8m/s × 10 s
= 80m
Total
= 40 + 20 + 80
=140m
20
Time (sec)
30
FORCES
Forces are pushes or pulls (a combination is a
twist).
Objects are stationary when forces are
balanced
gravity is always acting but we don’t keep
falling due to a support force
Forces can be measured using a Newton meter.
BALANCED FORCES
An unbalanced force causes changes to objects motion (speed or
direction), or shape.
If a force acts on a stationary object and causes motion, the object
has gained kinetic (movement) energy.
Friction will stop the object moving.
Types of force:
Gravity
Friction – the force that opposes motion
Magnetism
Tension – the force in rope, etc
Electrostatic
Support
Lift – in the air (planes/birds)
Bouyancy – in the water
FORCE PAIRS
Forces act in pairs (e.g.
thrust and friction, gravity
and support).
Force diagrams show the
forces acting on an object
and whether they are
balanced or unbalanced.
Force pairs
What are the
missing terms?
 Buoyancy
 Drag
 Thrust
 Weight

Newton’s

st
1
Law of Motion
An object at rest will remain at rest unless
acted on by an unbalanced force. An object
in motion continues in motion with the same
speed and in the same direction unless acted
upon by an unbalanced force.
Newton’s

nd
2
Law of Motion
Acceleration is produced when a force
acts on a mass. The greater the mass (of
the object being accelerated) the greater
the amount of force needed (to accelerate
the object).
Newton’s

nd
2
Law of Motion
EX: Mike's car, which weighs 1,000 kg, is
out of gas. Mike is trying to push the car to
a gas station, and he makes the car
accelerate at 0.05 m/s/s. Using Newton's
Second Law, compute how much force
Mike is applying to the car.
FORCE AND MOTION
What happens when you apply a small constant force to a
trolley and time it over a set distance?
Small constant
force
Set distance
The trolley should accelerate because…
An unbalanced force causes acceleration.
FORCE AND MOTION
What happens when you apply a small constant force to a
trolley carrying a 1kg mass and time it over a set distance?
Small constant
force
1Kg
Set distance
The trolley should accelerate but slower than previously
because…
The larger the mass the slower the
acceleration
FORCES AND ACCELERATION
Given the formula F = ma try the following questions.
1. What are the names and units of F, m and a?
2. Complete the table….
3. The rider and cycle are 150kg:
150N
800N
F
m
A
a.
9kg
0.5ms-2
6N
0.2kg
b.
c.
800g
1.5ms-2
350N d.
e.
15ms-2
1200kg 0.015ms-2
a. What is the Nett force?
b. What is the cyclist’s acceleration?
4. A bike accelerates at 10ms-2 using a force of 6000N. The
rider is 70kg. What is the mass of the bike?
WEIGHT FORCE
Weight is a force. It is therefore measured in… Newtons (N)
An object’s weight depends on two things…
Gravity
• varies depending where you are
• 10ms-2 or 10N/Kg on Earth
Mass
• does not vary
• measured in Kg
•A man with mass of 75Kg on earth weighs 750N
BUT on the moon he weighs 125N
The Source of Friction



Friction- A force that opposes motion
between 2 surfaces that are touching
Friction occurs because the surface of any
object is rough.
The amount of friction depends upon many
factors like:


Roughness of the surfaces
Force pushing the surfaces together
FRICTION
Friction can be reduced by…
lubrication,
streamlining (aerodynamics),
slowing down,
smoothing surfaces
Newton’s


rd
3
Law of Motion
For every action there is an equal and
opposite re-action.
Ex: Rocket Launching, Walking
UP,
UP,
and
AWAY!
Waves


Waves: a disturbance that travels through a
medium from one location to another often
transferring energy
Transverse: causes vibration in the medium
in a perpendicular direction to its own motion.


Example: Light, Electromagnetic spectrum
Longitudinal: have vibrations along or parallel
to their direction of travel.

Example: Sound
Waves

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

Wavelength: the distance between adjacent
crests, measured in meters.
Period: the time it takes for one complete wave
to pass a given point, measured in seconds.
Frequency: the number of complete waves that
pass a point in one second, measured in inverse
seconds, or Hertz (Hz).
As frequency increases, Wavelength decreases
Waves


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Refraction: the change in
direction of a wave due to
a change in its speed.
Wave speed varies in different media.
Sound waves travel faster in water than air.
(Sonar)
Light waves travel faster in air than water.
Electromagnetic Spectrum


Visible Light: ROY G BIV (Red has longer
wavelength.)
The range of all possible electromagnetic
radiation.

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What kind of electromagnetic radiation has the shortest
wavelength? The longest?
What kind of electromagnetic radiation could be used to
"see" molecules? A cold virus?
Why can't you use visible light to "see" molecules?
Some insects, like bees, can see light of shorter
wavelengths than humans can see. What kind of radiation
do you think a bee sees?
Earthquakes Making Waves

Seismic waves carry energy from an
earthquake away from the focus, through
Earth’s interior and across the surface.
Seismic Waves

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
Primary (P waves): can travel through all states of
matter through compressions and rarefactions much
like an accordion.
Secondary (S waves): cannot move through liquids;
move back and forth and up and down (transverse
wave)
Surface waves: when P and S waves reach the
surface


Love wave: rolls like a
wave
Rayleigh wave: shakes
side to side