Download Class Powerpoints- Chapter 4 11/14

Hewitt/Lyons/Suchocki/Yeh
Conceptual Integrated
Science
Chapter 4
MOMENTUM AND ENERGY
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This lecture will help you
understand:
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Momentum
Impulse
Impulse–Momentum Relationship
Conservation of Momentum
Work
Energy
Power
Potential Energy
Kinetic Energy
The Work-Energy Theorem
Kinetic Energy and Momentum
Conservation of Energy
Machines
Efficiency
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Momentum
Momentum—is ________ in _______
__________________________________
__________________________________
__________________________________
momentum = ____ ____
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Momentum
Momentum = ______  __________
or
Momentum = mass  ______ (_________________________)
Momentum = mv
_______
high
____ or high ______  high _________
______ and high velocity  higher
__________
_______ mass or low ________  low ____________
low mass and low velocity  lower momentum
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_______________
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Momentum
CHECK YOUR NEIGHBOR
A moving object has
A.
B.
C.
D.
momentum.
energy.
speed.
all of the above.
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Momentum
CHECK YOUR NEIGHBOR
When the speed of an object is doubled, its momentum
A.
B.
C.
D.
remains unchanged in accord with the conservation of
momentum.
doubles.
quadruples.
decreases.
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Impulse
Impulse- _______________________________
____________ for impulse:
Impulse = _______  _______ = ___
great force for ________ time  _________ impulse
same force for __________ time  __________ impulse
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Impulse
CHECK YOUR NEIGHBOR
When the force that produces an impulse acts for twice as
much time, the impulse is
A.
B.
C.
D.
not changed.
doubled.
increased by four times.
decreased by half.
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_______ - _________ Relationship
The __________ in ____________ of an
object is ________ to the _______ applied
to it __________ by the ________ interval
during which the ________ is ________.
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Impulse–Momentum Relationship
Equation:
___________ = change in momentum
or
______  ______ = ____ __________
_______ force, ______ change in velocity  ______
change in ________
_______ force for short time  ________ change in _________
_____ force for _______ time  ____ change in
_________
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Impulse–Momentum Relationship
Cases of momentum changes:
_____________ Momentum
____________________________________________
_____________________________________________
Examples:
__________ cannons have ___ barrels for ________
range
A golfer _______ _________ while teeing off
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Impulse–Momentum Relationship
CHECK YOUR NEIGHBOR
A cannonball shot from a cannon with a long barrel will
emerge with greater speed, because the cannonball
receives a greater
A.
B.
C.
D.
average force.
impulse.
both of the above.
neither of the above.
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Impulse–Momentum Relationship
Cases of momentum changes:
______________ Momentum
____________________________________________
____________________________________________
Examples:
_______ into a _________ versus a brick ______
_________ into a _______ net versus onto solid _____
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Impulse–Momentum Relationship
CHECK YOUR NEIGHBOR
A fast-moving car hitting a haystack or hitting a cement wall
produces vastly different results. Both experience
A.
B.
C.
D.
the same change in momentum.
the same impulse.
the same force.
A and B.
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Impulse–Momentum Relationship
CHECK YOUR NEIGHBOR
When a dish falls, will the change in momentum be less if it
lands on a carpet than if it lands on a hard floor? (Careful!)
A.
B.
C.
D.
No, both are the same.
Yes, less if it lands on the carpet.
No, less if it lands on a hard floor.
No, more if it lands on a hard floor.
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_______________ of Momentum
In _______ case, the _________ of a
system _________ _______ unless it is
________ on by ___________ forces.
A system will have the _______ momentum
_______ ______ and ______ the interaction
occurs. When the momentum does _____
change, we say it is ________________.
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Conservation of Momentum
Law of ______________ of ___________:
______________________________________
______________________________________
____________ form:
(_____ momentum) ___ =(____ momentum)___
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Conservation of Momentum
Collisions
When objects ______ in the __________ of
external forces,
_______________________________________________
Examples:
_________ collisions
_________ collisions
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Conservation of Momentum
Elastic collision
_____________________________________________
_____________________________________________
_____________________________________________
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Conservation of Momentum
Moving Ball A __________ Ball B, ______ at ___.
Ball A comes to ____, and Ball B moves ___ with
a ________ _____ to the ____ velocity of Ball A.
Momentum is ____________ from Ball A to Ball B.
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Conservation of Momentum
______________ collision
______________________________________
______________________________________
______________________________________
______________________________________
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Conservation of Momentum
CHECK YOUR NEIGHBOR
Freight Car A is moving toward identical Freight Car B that
is at rest. When they collide, both freight cars couple
together. Compared with the initial speed of Freight Car A,
the speed of the coupled freight cars is
A.
B.
C.
D.
the same.
half.
twice.
none of the above.
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Work
Work
is defined
______________________________________
_________________________________ (in the
same direction as the force).
______________________________________
______________________________________
______________________________________
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Work
Two things enter where work
is done:
• _____________ of force
• ___________ of something
___ that ________
Work done on the object
___________________ by the
________________________
________________________.
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Work
CHECK YOUR NEIGHBOR
If you push against a stationary brick wall for several
minutes, you do no work
A.
B.
C.
D.
on the wall.
at all.
both of the above.
none of the above.
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Work
The quantity of work done
________________________________________
____________________________ in the _______
in which the force acts.
Work falls into two categories:
• work done ______________ another force
• work done to ________ ____ ______ of an
object
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Work
CHECK YOUR NEIGHBOR
Work is done in lifting a barbell. How much work is done in
lifting a twice-as-heavy barbell the same distance?
A.
B.
C.
D.
Twice as much.
Half as much.
The same.
Depends on the speed of the lift.
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Work
CHECK YOUR NEIGHBOR
You do work when pushing a cart with a constant force. If
you push the cart twice as far, then the work you do is
A.
B.
C.
D.
less than twice as much.
twice as much.
more than twice as much.
zero.
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Energy
Energy
______________________________________
______________________________________
The _______ of _______ are observed only when
it is being _________ from ___ place to ______
or
_____________ from ____ form to _________.
Unit for energy: _________
Both _____ and _______ are measured in _____.
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Power
Power
____________________________________
or
the ______ at which ________ is _______ from
______ ________ to ______________.
Equation for power:
Power  work done
time interval
Units
for power: _________________, or ____

(One watt = 1 joule of work per second)
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Power
CHECK YOUR NEIGHBOR
A job can be done slowly or quickly. Both may require the
same amount of work, but different amounts of
A.
B.
C.
D.
energy.
momentum.
power.
impulse.
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Potential Energy
Potential Energy
is defined
______________________________________
____________. In its stored state, ________
has the ___________ for doing work.
Examples:
__________ bow
________________ rubber band
___________ ram of a pile driver
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Potential Energy
The amount of gravitational potential energy
possessed by an elevated object_________
_____________________________________
_____________________________________.
_____ done ______ _____ required to move it
_______  the _____ distance moved (______).
The upward force when moved at constant
velocity is the weight, _____, of the object. So
the work done in lifting it through ______ h is the
product mgh.
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_____________ Energy
Equation for gravitational potential energy:
PE = ________________
or
PE = ___________
_______________ potential energy examples:
Water in an ___________ reservoir
The elevated ram of a pile driver
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Potential Energy
CHECK YOUR NEIGHBOR
Does a car hoisted for repairs in a service station have
increased potential energy relative to the floor?
A.
B.
C.
D.
Yes.
No.
Sometimes.
Not enough information.
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Kinetic Energy
Kinetic Energy
is defined as the energy of a moving body
Equation for kinetic energy:
Kinetic energy = 1/2 mass  speed2
or
Kinetic energy = 1/2 mv2
small changes in speed  large changes in kinetic
energy
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Kinetic Energy
CHECK YOUR NEIGHBOR
Must a car with momentum have kinetic energy?
A.
B.
C.
D.
Yes, due to motion alone.
Yes, when motion is nonaccelerated.
Yes, because speed is a scalar and velocity is a vector quantity.
No.
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The Work-Energy Theorem
When work is done on an object to change its kinetic
energy, the amount of work done is equal to the change in
kinetic energy.
Equation for work-energy theorem:
Net work = __________________
• If there is ___ _________ in object’s energy, then __
work is done.
• Applies to ______________ energy: For a ________
held stationary, _____ further work is done  no
further change in _______________
• Applies to ______________ energy:
The more __________ energy something has  the
_________ work is ____________ to _________ it
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The Work-Energy Theorem
CHECK YOUR NEIGHBOR
Consider a problem that asks for the distance a fastmoving crate slides across a factory floor in coming to a
stop. The most useful equation for solving this problem is
A.
B.
C.
D.
F = ma.
Ft = mv.
KE = 1/2mv2.
Fd = 1/2mv2.
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The Work-Energy Theorem
CHECK YOUR NEIGHBOR
The work done in braking a moving car to a stop is the
force of tire friction  stopping distance. If the initial speed
of the car is doubled, the stopping distance is
A.
B.
C.
D.
actually less.
about the same.
twice.
none of the above.
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_________ Energy and Momentum
Comparison of _______ _______ and _________
• ______ depend on ______ and _________—
_________ depends on ______ and ______.
___ depends on ______ and the ________ of its
speed.
• _________ is a vector quantity.
________ energy is a ____________ quantity.
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____________ of Energy
__________________
is defined in everyday language as “______”—in
physics, to “______ ____________.”
_______ of ____________ of _________:
In the ___________ of ___________ work input
or output, the energy of a system remains
unchanged. _______ cannot be ________ or
__________.
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Conservation of Energy
A situation to ponder…
Consider the _______ of a _______ and
_________. In drawing the ______, we do
work on the system and give it ________
energy. When the bowstring is ________,
most of the ___________ energy is
_____________ to the arrow as ________
energy and some as _______ to the bow.
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A situation to ponder…
CHECK YOUR NEIGHBOR
Suppose the potential energy of a drawn bow is 50 joules,
and the kinetic energy of the shot arrow is 40 joules. Then
A.
B.
C.
D.
energy is not conserved.
10 joules go to warming the bow.
10 joules go to warming the target.
10 joules is mysteriously missing.
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_____________
Machine — a device for __________ force or
changing the __________ of force.
No machine can
• put out more ________ than is put into it.
• _________ energy; it can only transfer or
_____________ energy.
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Machines
Equation:
work ______ = work ______
(______  distance)___ =(____  distance)____
Example: a _______ lever
small input force over a ____ distance  large
_______ ______ over a _______ distance
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Machines
CHECK YOUR NEIGHBOR
In an ideal pulley system, a woman lifts a 100-N crate by
pulling a rope downward with a force of 25 N. For every
one-meter length of rope she pulls downward, the crate
rises
A.
B.
C.
D.
50 centimeters.
45 centimeters.
25 centimeters.
none of the above.
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Efficiency
Efficiency—
________________________________________
_______________________________________.
Equation for efficiency:
Efficiency  work done  100%
energy used
a machine with ___ efficiency  greater amount
of _____ wasted as heat
Some ______ is always _________ as heat, which
means that no machine is ever 100% ________.
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Efficiency
CHECK YOUR NEIGHBOR
A certain machine is 30% efficient. This means the
machine will convert
A.
B.
C.
D.
30% of the energy input to useful work—70% of the energy input
will be wasted.
70% of the energy input to useful work—30% of the energy input
will be wasted.
as strange as it may seem, both of the above.
none of the above.
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