Transcript Force_Motion - World of Teaching

Energy, Force, and Motion
identifying energy transformations;
Identifying and analyzing the transfer of heat energy by conduction,
convection, and radiation
interpreting a phase diagram; describing and calculating velocity and
acceleration;
comparing Newton’s three laws; calculating mechanical advantage;
understanding
the work of simple machines
Waves, Electricity, and Magnetism
investigating light and sound phenomena and comparing light to sound;
Doppler effect; describing the causes of static electricity; constructing and
analyzing
series and parallel circuits; describing the relationship between voltage, current
and
resistance and relating electricity and magnetism and common applications
SPEED
Describes how fast an object
is moving.
Average Speed =
distance
time
Velocity
The speed of an object in a certain
direction.
Velocity
d
V= t
speed of an object in a certain
direction.
V = velocity (meters/second)
d = distance (meters)
t = time (seconds)
Velocity
speed of an object in a certain
direction.
0
3 seconds 1
2
Speed=?
Velocity=?
Total time=
4 seconds
12 meters
20 meters
16 meters
Numerator
Denominator
5
12
Acceleration
Acceleration is how quickly
velocity changes over time.
X L eh ray shun
0
3 Speed
1
2
Meters/second
Acceleration
how quickly velocity changes over time.
(V
V
)
final
initial
A = ___________
time
Acceleration the change
in velocity over time.
Acceleration =
change in velocity
time
Acceleration =
V1 = beginning velocity
V2 = ending velocity
(v
–
v
)
2
1
________
Time
The graph below relates speed and time
of four cars (1, 2, 3, and 4) traveling
along a straight highway.
Which two cars move with zero
acceleration?
1 and 4
2 and 3
1 and 2
3 and 4
Which of the following is certain
to change as a ball accelerates?
mass of the ball
inertia of the ball
velocity of the ball
force acting on the ball
What must happen to an object in
order to accelerate it?
A net force must be applied.
Some weight must be removed.
Its frictional coefficient must be
reduced.
It must contain momentum.
Which of these describes the
object with the largest
acceleration ?
An object with a small change in
velocity over a small change in time
An object with a small change in
velocity over a large change in time
An object with a large change in
velocity over a small change in time
An object with a large change in
velocity over a large change in time
Scalar
a measurement that does
NOT contain direction.
Egg sample: Speed
Vector
a measurement that contains
direction.
Egg sample: Velocity
Forces of Nature
Gravitational
Magnetic
Mass and Inertia
The universe
consists of matter
in motion
The greater the mass
the harder it is to move.
And . . .
the harder it is to stop moving.
Lower mass objects are easier to move . .
.and to stop moving.
NEWTON’s Laws
1st Law of Motion :
An object remains at a
constant speed
in astraight path
,until a net force acts
on it.
NEWTON’s 1st Law of Motion
is the law of
ih ner shah
An object will
remain at a
constant speed
(unless disturbed).
the force of a
moving body.
the mass times velocity of an object
p=m•v
Momentum = mass x velocity
(Kgrams) (meters/second)
Momentum = mass x velocity
Higher mass higher momentum
Higher velocity higher momentum
p=m•v
includes velocity.
So, it has direction.
Momentum points in the
direction of motion.
Conservation of momentum
When objects collide, all of the
momentum goes somewhere.
Conservation of momentum
When objects collide, all of the
momentum goes somewhere.
Conservation of momentum
When objects collide, all of the
momentum goes somewhere.
Conservation of momentum
When objects collide, all of the
momentum goes somewhere.
NEWTON’s
nd
2 Law of Motion :
An object that
has a force
acting on it will
change its speed
(accelerate).
NEWTON’s
nd
2 Law of Motion :
f = m•a
force = mass • acceleration
f = net force (newtons)
m = mass (Kilograms)
a = acceleration (meters/second2)
NEWTON’s
nd
2 Law of Motion :
mass of the club
acceleration of the club
force of the club
f = m•a
Net force is the total amount of Force
(minus the forces that cancel each other
out).
Force of gravity
Force of muscles
Net force
When the net force is Zero.
-> NO movement
When the net force is NOT Zero.
-> movement
Static Equilibrium Balanced forces
When all forces are balanced.
The net force is Zero.
There is NO movement.
3 Kg
?
2 Kg
50 N
50 N
50 N
50 N
NEWTON’s
3rd Law of Motion:
For every action there is
an equal and opposite reaction.
NEWTON’s
3rd Law of Motion:
For every action, there is
an equal and opposite reaction.
NEWTON’s
3rd Law of Motion:
For every action, there is
an equal and opposite reaction.
Gravity
Action
Inertia
Friction
Balanced or unbalanced?
Reaction
UN balanced
Speed (m/s)
Gravity
BALL
Ground
Time (mSec)
Inertia
Speed (m/s)
UN balanced
PUTTER
BALL
Time (mSec)
Friction
Speed (m/s)
UN balanced
SKATE
Time (Sec)
A car is traveling down a hill. Which
of the following will affect the amount
of energy the car has?
how long the car is
the time of day
how much the car weighs
the color of the car
Friction
the resistive force that occurs
when two surfaces travel past
each other.
causes physical deformation
generates heat
Friction
the resistive
force that
occurs when
two surfaces
contact each
other.
Oliver the dog doesn't want to
walk in the rain. He can make his
owner pull harder on the leash to
get him out the door by
sitting on the vinyl floor.
sitting on the tile floor.
sitting on the carpeted floor.
sitting on the wood floor.
Pauline needs to measure the sliding friction of a
brick. How should she go about doing this?
attach the brick to a string and then to a spring
scale and read the force needed to quickly lift the
brick off the ground
drag the brick by a string attached to a spring scale
so that it gradually speeds up
drag the brick by a string attached to a spring scale
along the surface of a table at a constant speed and
read the force
hang the brick from a string attached to a spring
scale and read the force
Sliding friction-the drag force
created when the surface of one
object slides across the surface of
another object.
Sliding Friction Lab
Object
Surface
force (Newstons)
terminal velocity gravity will
accelerate an object until air
resistance (friction) does not
allow it to go any faster.
In the absence of air resistance,
which of these objects will fall at
the fastest rate when dropped?
the ball with a mass of 75 kg
the ball with a mass of 25 kg
the ball with a mass of 10 kg
They all fall at the same rate.
Pressure is the amount of force
exerted over a certain area.
Pressure = Force
Area
Pressure = Force (newtons)
Area (m2)
1 Pascal = 1 Newton/meter2
Distance{
W = f • d
Force
Distance
{
Gravitational force
Gravitational force
Gravitational force
o INCREASES with Mass
o DECREASES with Distance
All objects in the universe are
attracted to each other by the
force of
effort.
friction.
gravity.
inertia.
Four pairs of objects have the masses
shown below. If the objects in each pair
are the same distance apart, the
gravitational force between the objects
in which pair is greatest?
1 kilogram and 1 kilogram
1 kilogram and 2 kilograms
2 kilograms and 1 kilogram
2 kilograms and 2 kilograms
As an astronaut travels from Earth to a
space station orbiting Earth, what
happens to her mass and weight?
Her mass decreases, but her weight
remains the same.
Her mass increases as her weight
decreases.
Her mass remains the same, but her
weight decreases.
Her mass decreases and her weight
also decreases.
Which hill would you slide down
the fastest?
hill A
hill B
hill C
It would take the same time to
slide down all of the hills.
Projectile
Motion
Velocity (m/s)
forward
downward
50 39.2
19.6
29.4
9.8
0
0
3 seconds 1
2
Projectile
Motion
Velocity (m/s)
forward
downward
46
47
48
49
50 39.2
19.6
29.4
9.8
0
0
3 seconds 1
2
Simple Machines and work
Lever
Inclined plane
Pulley
Wedge
Screw
Wheel and axle
Simple
Machines
• Pulley
• Wheel &
Axle
• Lever
• Inclined plane
• Screw
• Wedge
• Gear
Simple Machines
Pulley
Inclined plane
Wheel & Axle
Screw
Lever
Wedge
Gear
Which activity involves the use of
a simple machine?
riding on a seesaw
flying a kite
listening to a radio
skiing down a hill
Simple Machine
A mechanism that lowers
the amount of force needed
to do work, by increasing
the distance.
On which simple machine is a
fulcrum found?
pulley
wheel
axle
lever
ALL Simple Machines
work the same way
Lever action
2 meters
1 meter
Force=13 N
Force= ?
Mechanical
Advantage= final distance
starting distance
9 meters
3 meters
Mechanical
Advantage= distance
distance
8 meters
2 meters
Which of the following is often
used as a lever?
file
nail
saw
crowbar
The Wedge
The bottom of this light bulb is
an example of what type of
simple machine?
a lever
a pulley
a screw
a wedge
What type of simple machine is
used to split things apart?
screw
wheel and axle
wedge
inclined plane
What type of simple machine is
used to pull a flag up to the top
of a flagpole?
screw
wheel and axle
inclined plane
pulley
Pulley Lab
A fixed pulley
B movable pulley
C double pulley (end in top)
D double pulley (end in bottom)
DO THIS FIRST!
Hook on
Bottom
dude !
Force of the weight
ONLY.
A.
fixed pulley
Get out your own sheet of paper
1. Write down the force of the
weight (newtons).
2. For each pulley system write
down the NEW force of
the weight.
•
Pull the string exactly 20
cm.
•
Write down the distance
C. double pulley (end in top)
(cm) that the weight
(end in bottom)
moved.
•
Calculate the mechanical
B. movable pulley
D. double pulley
BIG Teeth=16
small Teeth =8
16:8
2:1
So, the small gear
spins TWICE AS FAST
as the big gear.
A 200 pound man lifts a rock weighing
800 pounds by standing on the end of
a lever. calculating
How much mechanical
advantage did the lever provide ?
mechanical
M.A. = 800
Kg/200 Kg = 4
Advantage
If you wuz ‘n a
Merry-go-round
& yuz let go,
Which wayz wud yu go?
Centripetal force
The inward force
on a spinning object,
that stops it
from going in
a straight line.
Perpendicular
Centripetal force
Centripetal force
sen tripit ul
The inward
force
on a
Spinning
object.
Centripetal force
The
inward force
on a
Spinning
object.
Satellites stay in place as they orbit
because of . . .
the repeated firing of rocket
boosters.
the gravitational pull of Earth.
a narrow path through the vacuum
of space.
solar panels generating energy to
hold them in place
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