Download Chapter 9 Notes

Chapter 9 Notes
I. Work, Power, and Machines
A. What is _____?
1. measures the effect of a ______
2. must act over a _________
3. lots of force can be ________, but __ work done  how?
4. formula:
5. work is measured in ______  SI Unit
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B. Power
1. measures the _____ at which _____ is done
2. determined by how _____ or _____ work is completed
3. formula:
4. power is measured in ______  SI Unit
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C. Machines and mechanical advantage
1. machines ____ us do work by ____________ the work that
we ____ ____ them
a. machines can ______ the __________ of a force
b. machines can greatly _______ an ______ force by
changing the ________ over which the ______ is applied
2. different _______ can do the _____ amount of work
a. lifting a box straight up requires a ______ force over a
______ distance
b. using a ramp to lift a box requires a ________ force
over a ________ distance
3. mechanical advantage tells how much a machine
__________ force or ___________ distance
a. MA is a ratio between ______ and ______ forces
b. formula:
c. __ SI Unit  it is a ______
d. HINT: all answers should be ________ than ____
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II. Simple Machines
A. Broken down into ____ main categories
1. the ______ family
2. the _________ ______ family
B. The ______ family
1. levers are divided into three classes
a. 1st class
b. 2nd class
c. 3rd class
2. ________ are modified levers
a. single fixed pulley  _________
b. single moveable pulley  _________
c. multiple pulleys  even higher mechanical advantage
d. hint: look at the ________ of ________ force ropes
bearing the load
e. multiple pulley systems are often called a ______
____ _______
3. a ______________ is a lever or pulley connected to a shaft
a. wheel turns  axle also turns
b. small input force  large output force
c. example: steering wheel of a car
C. The _____________ family
1. inclined planes __________ and _________ force
a. changes __________ and ___________ of force
b. example: wheelchair ramp
2. a _______ is a modified inclined plane
a. functions like two inclined planes back to back
b. ____ ___________ force becomes ____ forces
directed out to the ______
c. example: axe blade
3. a screw is an inclined plane wrapped around a ___________
a. threads of a screw  inclined plane
b. _________ threads  more _______ force required
D. Compound machines
1. machine made up of more than one simple machine
2. examples:
a. pair of scissors  two ___________ joined at a
_________; each lever has a _______ for a blade
b. car jack  _____ in combination with a large ______
III. What is Energy?
A. Important Concepts
1. whenever _____ is done, _______ is transferred or
transformed to another system
2. energy can be present in an object or system even when
nothing is happening
3. because ______ is a measure of the _______ to do _____,
energy and work are both expressed in _______
B. Potential energy
1. observations
a. stretching a rubber band requires _____
b. releasing a stretched rubber band  ___________
c. energy used to _______ the rubber band is ______ in
the rubber band  able to do _____ at a ______ time
d. where is the energy before you release it?
2. potential energy is ______ energy
a. common names include:
1) _______ energy
2) energy of _________
3) energy of ____
b. types of potential energy
1) ________ potential energy  ____________
2) __________ potential energy  ____________
3) _________ potential energy  _________/
_______________
3. gravitational potential energy depends on both _____ and
_______
a. because it results from the ______ of ________, GPE
depends on the _____ of the objects in a system and on
the _________ between them
b. formula:
c. note that GPE is measured in _______  SI Unit
d. also note that “mg” in the equation is the _______ of
the object  _____ = _______ x _______
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C. Kinetic energy
1. observations
a. apple falls from the branch of a tree  ________ to
do _____
b. energy of a moving object  _______
2. kinetic energy depends on _____ and _____
a. falling apple > falling cherry
Why?
b. apple falls  kinetic energy _________ Why?
c. formula:
3. kinetic energy depends on ______ more than mass
a. because speed is ________, a greater value for speed
will cause a ______ increase in KE
b. example: violence of a car crash
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D. Other forms of energy
1. mechanical energy
a. sum of _________ and _________ energy
b. ___ = ___ + ___
2. atoms and molecules have kinetic energy
a. all atoms are ___________ in motion
b. can be affected by ____________
3. chemical reactions involve __________ energy
4. living things get energy from ________
5. the sun gets energy from ______ reactions  ______ _____
6. ___________ is a form of energy
7. ______ can carry energy across empty space
IV. Conservation of Energy
A. Energy transformations
1. ________ energy can become _______ energy
2. _______ energy can become _________ energy
3. energy transformations explain several everyday occurrences
a. a _________ ball
b. the ________ of a ball
4. mechanical energy can change to other forms of energy
a. elastic PE  ________ energy
b. heat energy  result of _______ (___)
B. The law of conservation of energy
1. energy cannot be ________ or __________
2. energy does not simply ________ or _________
3. systems may be _____ or _______
C. Efficiency of machines
1. not all of the work done by a machine is ________ work
a. _______  _____
b. _______
2. efficiency is the ______ of useful work to work in
a. ___ SI unit
b. formula:
c. ___ machine is _____ efficient
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