Transcript EOY_Force_and_Motion_PP[1]

Potential vs. Kinetic
 Potential
 * GPE
 * stored energy
 * not moving
 * the higher the object
the more PE
 * GPE=mgh
G= 9.8 m/s2
Kinetic
* KE
* energy of motion
* moving
* the faster an object
the more KE
* KE=mv2
Mechanical vs. Chemical
 Mechanical
Chemical
• ME = PE+KE
• Physical change
• Only changes the physical
appearance
• Ex. Gears moving in a car
• Energy that is moving
* Chemical change
* changes the
composition
* Ex. food being broken
down
* energy that is stored
Sample Question
 A 21.7 kg ball is located on a shelf 1.6 m above the
ground. Which best describes the energy of the ball?
A. Its energy is lost once it falls off the shelf
B. Its energy depends upon the speed the ball will travel
C. It has mechanical energy in the form of potential
energy
D. It has mechanical energy in the form of kinetic
energy
Sample Question
 What happened to the ball’s energy from Point 1 to
Point 4?
A. Stored Energy was transformed into energy of
motion
B. Energy of motion was transformed into chemical
energy
C. Stored energy in the ball applied a force to get the
ball to move
D. Internal energy caused the ball to move until the
energy was gone
Sample Question
 As a roller coaster car travels down a hill, which type of
change in energy allows it to speed up?
A.
Potential energy changing into heat energy
B.
Potential energy changing into kinetic energy
C.
Kinetic energy changing into heat energy
D.
Kinetic energy changing into potential energy
Types of Energy
 Electrical: energy that is transferred by electrical charges
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or current
Sound: associated with vibrations of matter and requires
an object to travel through (Medium). Ex. Water
Solar: the energy given off by the sun
Chemical: energy that is stored in the chemical
composition of matter
Thermal: the energy given off by heat
Light: energy given off by light
Nuclear: the potential energy stored in the nucleus of an
atom
Sample Question
What form of energy does a car’s engine convert into
mechanical energy?
A. Light
B. Wind
C. Chemical
D. Gravitational
Sample Question
Which type of energy is changed by plants into chemical
energy?
A.
Solar
B.
Nuclear
C.
Thermal
D.
Gravitational
Simple Machines
Type
Definition
Lever
A solid bar that
rotates around
a fulcrum
Inclined Plane
A flat horizontal
or sloped ramp
Pulley
Wheel & Axle
Wedge
Screw
Example
Wheelbarrow
A wheel that
turns on an axle
Handicap
ramp
Crane,
gears
A wheel that is
fixed to a pulley
Car or
gears
2 incline
planes that are
together
screwdriver
An incline plane
wrapped around
a shaft
Spiral stairs
or meat
grinder
Mechanical
Advantage
ratio of the length of the lever on
the applied force side of the fulcrum
to the length of the lever on the
resistance force side of the fulcrum
ratio of an input force
to an output force
equal to the number of
ropes that support the
moveable pulley
Radius of the wheel
divided by the radius of
the axle
ratio of the length of
its slope to its width
Sample Question
How can an inclined plane make work easier?
A. By increasing the amount of friction necessary for
the task
B. By increasing the effort necessary to raise an object
C. By decreasing the effort required to raise an object
D. By decreasing the efficiency of the task
Sample Question
Which simple machine would be the most efficient for
lifting an object 30m off the ground?
A. Pulley
B. Screw
C. Wedge
D. Lever
Force and Motion Important Terms
 Position: location (can be an object or place)
 Reference Point: location that you compare your
object or place’s position
 Motion: change of position over time
Forces and Motion Terms
 Speed: the measure that something moves in a given
amount of time speed=distance/time
 Velocity: speed in a specific direction
velocity=distance/time
 Acceleration: the rate at which velocity changes with
time acceleration=velocity final- velocity initial/time
Force and Motion Important Terms
 Friction: force that resists the motion between two
surfaces in contact.
 Force: a push or pull (F= M x A)
 Balanced force: net force is zero, the motion of an
object does not change
 Unbalanced force: changes the motion of an object
 Inertia: the resistance of an object to a change in the
speed or direction of its motion
Newton’s
st
1
Law of Motion
 An object at rest stays at rest, and an object in motion
stays in motion at the same velocity, unless acted upon
by an unbalanced force.
 Newton’s First Law is also called the Law of Inertia.
 Inertia is closely related to mass. When you measure the
mass of an object, you are also measuring its inertia.
 The more mass something has, the harder it is to change its
motion.
 Ex: It’s easier to stop an empty wagon than a wagon full of
sand.
nd
2
Law of Motion
 Acceleration of an object increases with increased force and
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decreases with increased mass.
The direction in which an object accelerates is the same as the
direction of the force.
Simply put: Newton’s Second Law is…
F = ma
(Force = mass x acceleration)
The standard unit of force is the newton (N).
Because force = mass x acceleration, force is measured in units of
mass (kg) times units of acceleration (m/s2).
A newton is the amount of force that it takes to accelerate 1 kg of
mass 1 m/s2.
So…. I N = 1 kg x 1 m/s2.
Sample Question
John wants to build a racetrack that will allow his toy
cars to travel fast when force is applied. Which
material should be use?
A. carpet, because friction will be high
B. Gravel, because friction will be high
C. Plastic, because friction will be low
D. Sandpaper, because friction will be low
rd
3
Law of Motion
 Forces always act in pairs!
 Newton’s Third Law: For every action, there is an
equal and opposite reaction.
 Every time one object exerts a force on another
object, the second object exerts a force that is
equal in size and opposite in direction back on the
first object.
Sample Question
A magnet is placed near a pile of steel paper clips. Which
will most likely occur?
A. The magnet will provide a balanced force, causing
the paper clips to spin in circles.
B. The magnet will provide an unbalanced forces,
keeping the paper clips stationary.
C. The magnet will provide a balanced force, pushing
the paper clips away from it.
D. The magnet will provide an unbalanced force,
pulling the paper clips toward it.
Summary of Newton’s 3 Laws
Distance/Time Graphs
The motion of an object can be represented in a line graph. The data table
below charts the motion of an object in 20 seconds.
Construct a line graph on page 28 (blank page) that shows the motion of
the object. Be sure to label both axes.
Then, use the graph to describe the motion of the object between 0 and 10
seconds.
Distance vs. Time
Time (s)
0
5
10
15
20
Distance
(m)
0
10
10
15
20
Sample Question
Which describes their
motion?
Steven threw four balls into the
air and recorded their
heights. The chart below
shows the maximum height
for each ball.
Ball Maximum Height (m)
M
2.0
N
1.5
O
4.2
P
3.0
A. Ball P went twice as high as
Ball N
B. Ball M went twice as high as
Ball N
C. Ball P went two meters
higher than Ball O
D. Ball N went two meters
higher than Ball O
Sample Question
The chart shows the distance traveled by an object over
100 seconds.
What happened to the motion of the object between
t=50s and t=70s?
A. The object increased its speed
B. The object decreased its speed
C. The object stopped moving
D. The object changed directions
Sample Question
Which graph represents a moving object with a constant
speed throughout its entire travel time?