Transcript Newton`s Laws powerpoint

TAKS Objective 5
Motion , Forces
and Energy
4A
• calculate speed, momentum,
acceleration, work, and power in
systems such as in the human body,
moving toys, and machines
• Use the formula chart to help
determine these answers!
Griddable Answers
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Some of the
problems
require you to
grid in an
answer. Make
sure you pay
attention to
the decimal
point in the
square in the
middle.
Definition of a Force
• A Force is a
push or a pull
Balanced Force
• A force that
produces no
change in an
object’s motion
because it is
balanced by an
equal, opposite
force.
Unbalanced Forces cause
changes in motion
Work
• Work: using a force
for a distance
• W=Fxd
• The work done by forces on an
object = changes in energy for
that object.
• Work and Energy are measured in
Joules
How much work is performed when a 50 kg crate is
pushed 15 m with a force of 20 N?
F 300 J
G 750 J
H 1,000 J Use the formula Work = Force x
J 15,000 J distance
Force of 20 N x 15 meters = 300
Joules
The diagram represents the total travel of a
teacher on a Saturday. Which part of the trip is
made at the greatest average speed?
FQ
How do we work this one?
GR
HS
Calculate v = d/t for each segment.
J T
Real Machines use Energy
• No real machine is
100 % efficient. i.e.
none put out more
work than is put in
• Efficiency of a
machine is work
output/work input
X 100 %
• Eff = Wout X 100%
W
in
The diagram shows an
electric motor lifting
a 6 N block a distance
of 3 m. The total
amount of electrical
energy used by the
motor is 30 J. How
much energy does the
motor convert to
heat?
F 9J
See Next Slide
G 12 J
for Answer
H 18 J
J 21 J
Work
Input =
30J done
by the
motor
Work Output =
Resistance Force x
Resistance Distance
Workout = 18J = 6N x 3m
The difference is lost as
heat due to friction, which
is 30J – 18J = 12J
Answer G
A ball moving at 30 m/s has a
momentum of 15 kg·m/s. The mass
of the ball is —
A 45 kg
B 15 kg
C 2.0 kg
D 0.5 kg
Formula Page says that
Momentum = Mass x Velocity
So 15 kg.m/s = M x 30 m/s
solving for M it is:
An advertisement claims that a certain truck
has the most powerful engine in its class. If
the engine has more power, which of the
following can the truck’s engine do, compared
to every other engine in its class?
F Produce fewer emissions
G Operate more efficiently
HINT: Look at the
formula for Power
H Perform work faster
J Accelerate longer
HINT: An object in
motion can have a
constant velocity,
constant momentum,
and constant
acceleration BUT it
cannot travel any
distance other than
ZERO & still be at
rest!
4B
• investigate and describe applications
of Newton's laws such as in vehicle
restraints, sports activities,
geological processes, and satellite
orbits
Friction
Friction causes an
object to slow
down and stop.
Since the amount
of energy stays
constant, the
energy becomes
heat.
Newton’s 1st Law of
Motion
• Object in
motion stays
in motion
• And Objects at
rest stay at
rest
• Unless acted
upon by an
unbalanced
force
Inertia or Newtons 1st Law
• Tendency for an
object to stay at rest
or keep moving in a
straight line at a
constant speed.
• The mass (m
measured in kg) of an
object determines its
inertia
• More mass = more
inertia
Newton’s 2nd Law of Motion
The greater the
mass of an
object, the
greater the
force required
to change its
motion.
F=mXa
The frog leaps from its resting position at the lake’s
bank onto a lily pad. If the frog has a mass of 0.5 kg
and the acceleration of the leap is 3 m/s2, what is the
force the frog exerts on the lake’s bank when
leaping?
A 0.2 N
B 0.8 N
C 1.5 N
D 6.0 N
Formula chart says F=ma, m is mass in
kg, a is acceleration in m/s2.
So, .5 kg x 3 m/s2= 1.5 N
Newton’s 3rd Law of
Motion
• For every
action force
there is an
equal and
opposite
reaction
force.
Newton’s 3rd Law of
Motion
All forces come in
action-reaction
pairs
Ex: feet push
backward on floor,
the floor pushes
forward on feet
Starting from rest at the center of a
skating rink, two skaters push off from
each other over a time period of 1.2 s.
What is the force of the push by the
smaller skater?
F 16 N
Newton’s 3rd law
states that forces are
G 32 N
equal & opposite in
H 88 N
direction
J 100 N
4D
• investigate and demonstrate
mechanical advantage and efficiency
of various machines such as levers,
motors, wheels and axles, pulleys, and
ramps
Machines use power
• Power: the rate
at which energy
is used (work is
done)
• P=Work/time
• Power is
measured in
watts
If a force of 100 newtons was
exerted on an object and no work
was done, the object must have —
A accelerated
rapidly
B remained
motionless
C decreased its
velocity
D gained momentum
Work = Force x Distance
Work = 0
so
Force = 100 N
0 J = 100 N x d
distance must be 0
It did not move!
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6 Types of simple
machines
Inclined planes
Screws
Pulleys
Wheel and axle
Levers
Wedge
The diagram shows an electric motor lifting a 6 N block a
distance of 3 m. The total amount of electrical energy used by
the motor is 30 J. How much energy does the motor convert to
heat?
F 9J
G 12 J
H 18 J
J 21 J
Which configuration of pulleys and
belts shown below will result in the
fastest rotation of Spindle 2?
HINT: Both spindles
have to travel the
same distance over the
same time (speed =
d/t)
SO
•Larger spindle #1 will
cause a smaller spindle
#2 to travel faster
HINT: Work =
Force x
Distance
Which diagram
has equal
amounts of work
done on each
side of the
lever?
5A & 5B
• demonstrate wave types and their
characteristics through a variety of
activities such as modeling with ropes and
coils, activating tuning forks and
interpreting data on seismic waves;
• demonstrate wave interactions including
interference, polarization, reflection,
refraction, and resonance within various
materials
Waves - 2 Types
Transverse Waves
• Particles vibrate at
right angles to the
direction the wave
travels. (up & down
motion)
• Ex. E. M. Waves,
waves on a slinky or
rope coil, ocean
Longitudinal or
Compression Waves
Vibrating particles move
back and forth along
the direction of the
wave velocity
Parts consist of
compressions and
rarefactions
All waves have similar properties
• Frequency- the number of vibrations
per second or the speed of the
movement of the vibrating particles
– Frequency = pitch of sound = color of light
• Amplitude – the size of the movement
of the vibrating particles
– Amount of energy
– Ex: increased amplitude = louder sound
= brighter light
• Resonance – vibration in one object
causes a vibration in another nearby
object
Velocity: v=f λ
f-frequency and λ is
wavelength (distance
between identical points on
two consecutive waves)
Reflection- bounce off
barriers in regular ways
Refraction- waves can
change direction when
speed changes = bending
of wave
6A
• describe the law of
conservation of energy
Law of Conservation of
Energy
• Energy can change forms, but
is never created nor destroyed
• Loss in one form = gain in an
another form
• A falling object speeds up as it falls
to the ground; PE decreases as KE
increases. The KE it has at impact
= the PE it had before it fell.
Energy can be conserved
all forms
The chemical energy in a
battery transforms into
electrical energy
Energy
Is defined as the Ability
to do Work
Energy has Two Types:
Kinetic (Energy of Motion) and
Potential (Stored Energy)
Use the formula chart!!
Use the
formula
page!
PE = mgh
g=gravity = 9.8
m/s2
6B
• investigate and demonstrate the
movement of heat through solids,
liquids, and gases by convection,
conduction, and radiation
Heat- Transfer of Thermal Energy
Three forms of heating:
1. Conduction- direct
contact, a pot heating on a
stove (solids)
2. Convection- heating by
circulating fluids, (gas and
liquid) heating from a
fireplace
And. . .
3. Radiation – Transfer of
Electromagnetic (E.M.) Energy
• Objects are heated when
exposed to infrared
radiation
• The sun’s heats the earth
by sending infrared
radiation along with other
forms of E.M. energy
6D
• investigate and compare economic
and environmental impacts of using
various energy sources such as
rechargeable or disposable batteries
and solar cells
Nuclear Reactions
Fusion occurs when two atoms
combine to form a new
element.
The sun produces all of its
energy through fusion.
Fission is the splitting of nucleii
of large atoms such as
Uranium and Plutonium
Which of these produces most of the
compounds responsible for causing acid
rain?
A Nuclear fission
B Fossil fuels
C Solar cells
D Windmills
6E
• investigate and compare
series and parallel circuits
Series Circuits
• Series circuits are
the most simple.
• One (1) path for the
current to travel.
• Contains an energy
source, a path, and
a load (something
for it to do, like a
lamp)
Parallel Circuits
• Parallel circuits
provide more than
one path for the
current to travel.
• Most circuits are
parallel, since if
one lamp goes out,
the others can
stay lit.
For Voltage Mathematics - USE
THE FORMULA SHEET!!
• What is the current in a copper wire
that has a resistance of 2 ohms and is
connected to a 9 volt electrical
source?
V=IR
A. 0.22 amp
V = voltage = volts
B. 4.5 amps
I = current = amps
C. 11.0 amps
R = resistance = ohms
D. 18.0 amps
9V = I x 2 ohms or 4.5
amps
Which circuit is built so that if
one light bulb goes out, the
other three light bulbs will
continue to glow?
HINT: Check to see
which ones have
complete pathways for
each bulb!
Now You Try It!
Remember:
must have
complete
pathways
When a DVD is read, laser light touches
the DVD surface and is then measured at
location A. What allows light to return to
location A after striking the DVD surface?
F Conduction
G Refraction
H Magnification
J Reflection
An empty cup was tightly covered with plastic
wrap, and a few grains of salt were sprinkled
on top of the plastic. When a tuning fork was
struck and placed slightly above the plastic
wrap, the salt began to move. Which
characteristic of waves does the movement
of the salt best demonstrate?
A Echo formation
B Diffraction
C Resonance
D Specular reflection
HINT: All the types
of radiation MUST
equal the radiation
coming in
Assuming the chart contains all energy
transformations in the Earth system, how much
solar radiation goes toward evaporating water?
F
G
H
J
40,000 terajoules
92,410 terajoules
121,410 terajoules
133,410 terajoules
The weight lifter used a force of 980 N to
raise the barbell over her head in 5.21
seconds. Approximately how much work did
she do in raising the barbell?
F 380 J
G 982 J
H 2,000 J
J 10,000 J
What is the net force exerted on a 90.0 kg
race-car driver while the race car is
accelerating from 0 to 44.7 m/s in 4.50 s?
F 9.8 N
G 20 N
H 201 N
J 894 N
When the air is released from a balloon, the
air moves in one direction, and the balloon
moves in another direction. Which statement
does this situation best illustrate?
F What goes up must come down.
G For every action there is an equal and
opposite reaction.
H The shape and size of an object affect air
resistance.
J The acceleration due to Earth’s gravity is
9.8 m/s 2.