Download Chapter 3 Notepacket

Chapter 3 Newton’s First Law of Motion – Inertia
Chapter 3 Homework:
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Pg. 41 #8, 10-20
Pg. 42 #21-27, 30
Pg. 43 #35, 37, 40, 41
Pg. 44 # 44-48
Pg. 45 #51-55
Objectives:
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Describe Galileo’s idea about when a force is needed to keep an object moving.
State Newton’s First Law of Motion
Describe the relationship between mass and inertia
Explain how the law of inertia applies to objects in motion.
The Big Idea: Forces cause changes in motion
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A ball at ___________________ in the middle of a flat field is in
______________________. No net force acts on it. If you saw it begin to
______________ across the ground, you’d look for forces that don’t
_________________________ to zero. We don’t believe that changes in motion occur
without cause.
Lesson 3.3 Galileo in Motion
1. Galileo argued that only when _______________________ is present – as it usually is –
is a force needed to keep an object ______________________.
a. One of Galileo’s great contributions to physics was demolishing the notion that a
force is necessary to keep an object moving.
2. Friction is the name given to the force that acts between materials that
____________________ as they move past each other.
a. Frictional forces act on 2 objects which are in _______________________ when
on object _________________ or attempts to move
i. Act _____________________ to contact surface
ii. Act _____________________ direction of motion
b. Friction is caused by ___________________________ in the surfaces of objects
that are touching.
c. Even very _____________________ surfaces have microscopic irregularities that
obstruct _______________________.
d. If friction were absent, a moving object would need no force whatsoever to
remain in __________________.
e. Friction also depends on the _____________________ force.
i. Friction is ____________________ for heavier objects.
3. In terms of net force, friction opposes _______________________ and therefore would
be ________________________ from any force moving an object.
**Net force = force moving object
forward – force of friction
4. Galileo tested his idea by rolling balls along plane surfaces tilted at different
_______________________.
a. A ball rolling down an inclined plane ___________________ ___________.
b. A roll rolling up an inclined plane – in a direction opposed by
_______________________ - ________________ ________________.
c. A ball rolling on a smooth ____________________________ plane has almost
____________________ velocity.
5. Galileo stated that if friction were entirely absent, a ball moving
_____________________________ would move ______________________.
a. No __________________ or ____________________ (force) would be required to keep
it moving once it is set in motion.
6. Galileo stated that this tendency of a moving body to keep ____________________ is natural
and that every material object ______________________ changes in its state of motion.
7. The property of a body to resist changes to its state of motion is called
_______________________.
8. Concept Check: According to Galileo, when is a force needed to keep an object moving?
Lesson 3.4 Newton’s Law of Inertia
9. Newton’s first law states that every object continues in a state of __________________, or in
uniform speed in a ______________________ line, unless acted on by a
____________________ net force.
10. Newton’s first law, usually called that law of ______________________, is a restatement of
Galileo’s idea that a force is not needed to keep an object moving.
11. Objects at ________________
a. Objects in a state of rest tend to remain at _____________________.
b. Only a _______________ will change that state.
12. Objects in _________________________
a. In the absence of forces, a moving objects tends to move in a straight line
__________________________.
b. Toss an object from a space station located in the vacuum of outer space, and the object
will move _____________________ due to ________________________.
13. Blasts of air from many tiny holes provide a nearly ___________________-________________
surface on an air hockey table. If you slide a hockey puck along the surface of a city street, the
puck soon comes to __________________. If you slide it along an air hockey table where
_______________ is practically absent, it slides with no apparent loss of __________________.
14. The law of _______________________ provides a completely different way of viewing motion
from the ancients.
a. Objects continue to ______________________ by themselves.
b. ____________________ are needed to overcome any friction that may be present and
to set objects in motion __________________________.
c. Once the object Is moving in a ____________________-________________
environment, it will move in a straight line indefinitely.
15. Think! A force of gravity between the sun and its planets holds the planets in orbit around the
sun. If that force of gravity suddenly disappeared in what kind of path would the planets move?
16. Think! Is it correct to say that the reason an object resists change and persists in its state of
motion is that it has inertia?
17. Concept Check: What is Newton’s first law of motion?
Lesson 3.5 Mass – A Measure of Inertia
18. The more ____________________ an object has, the greater its __________________________
and the more _______________________ it takes to change its state of
___________________________.
19. The amount of inertia an object has depends on its ____________________- which is roughly
the amount of material present in an object.
20. _______________________ is the measure of the inertia of an object.
21. In other words, objects of _______________________ mass require greater
_____________________ to start moving or stop moving.
a. You can tell how much matter is in a can when you kick it. Kick and empty can and it
moves. Kick a can filled with sand and it doesn’t move as much.
22. Mass is NOT ________________________.
a. __________________________ is the measure of space and is measured in units such
as cubic centimeters, cubic meters, and liters.
b. Mass is measures in the fundamental unit of _____________________________.
23. Which has more mass, a feather pillow or a common automobile battery?
a. Clearly an automobile battery is more difficult to set in _________________________.
This is evidence of the battery’s greater _________________________ and hence its
greater _____________________.
b. The pillow has a larger size (__________________________) but a smaller mass than
the battery.
24. Mass is NOT __________________________.
a. Mass is often confused with weight.
b. Mass is more ________________________ than weight.
c. Mass is the measure of the amount of _______________________ in an object.
d. Weight is a measure of the _________________________ ___________________ acting
on the object.
e. Mouse says: Mass is a property ____________________ the body. Weight is an
__________________ force on the body.
25. Mass is Inertia
a. The amount of matter in a stone is the same whether the stone is located on Earth, on
the moon, or in outer space.
i. The ____________________ of the stone is the same in all these locations.
ii. The ____________________ of the stone would be very different on Earth and
on the moon, and still different in outer space.
iii. Weight is dependent on _________________________, mass is NOT.
iv. The stone’s inertia, or mass, is a property of the stone and not its
_________________________.
v. It’s just as difficult to shake a stone in its ____________________________
state as it is in its ____________________ state on Earth.
26. Mass and Weight
a. _____________________ is the quantity of matter in an object. More specifically, mass
is a measure of the inertia, or _________________________, that an object exhibits in
response to any effort made to start it, stop it, or otherwise change its state of
______________________.
b. __________________________ is the force of _________________________ on an
object.
c. Mass and weight are ________________________ to each other in a given place.
i. In the same location, twice the mass weighs ____________________________
as much.
ii. Mass and weight are proportional to each other, but they are not
_____________________ to each other.
27. Weight
a. The SI (standard international) unit of force is the ______________________. The SI
symbol for the newton is ________________.
b. One newton is equal to slightly less than a quarter _________________________.
c. If you know the mass of something in kilograms and want its weight in newtons at
Earth’s surface, ______________________ the number of kilograms by
___________________.
d. W = mg
i. “w” represents ___________________, “m” represents
____________________, and “g” represents ________________________ due
to _______________________.
e. One kilogram of nails weighs __________________ newtons, which is equal to
______________________ pounds.
f. Away from Earth’s surface, where the force of gravity is less, the bag of nails weighs
______________________.
g. When determining the weight of an object, use the formula W = mg
i. “m” must always be in units of ____________________ (if not convert)
ii. “g” must always be in units of ___________________.
1. If you are on the moon, then “g” is the acceleration due to gravity on
the moon
2. If you are on Mars, then “g” is the acceleration due to gravity on Mars.
3. On Earth, the __________________________ you go away from the
____________________, the smaller “g” will be.
4. On Earth’s surface, g = 10 m/s2.
28. Try it Out1
a. How much does a 20 kg dog weigh on Earth?
b. How much does a 35 kg human weigh on the moon where the acceleration due to
gravity (g) is 2.8 m/s2?
c. On Earth a sumo wrestler weighs 65 N, what is his mass?
d. If a person weighs 45 N on Earth, what would they weigh on Jupiter where the
acceleration due to gravity (g) is 10.7 m/s2?
e. On Venus, a car weighs 800 N and has a mass of 150 kg, what is the acceleration due to
gravity on Venus?
29. Think! Does a 2-kilogram bunch of bananas have twice as much inertia as a 1-kilogram loaf of
bread? Twice as much mass? Twice as much volume? Twice as much weight, when weighed in
the same location?
30. Concept Check: What is the relationship between mass and inertia?
Lesson 3.6 The Moving Earth Again
31. The law of inertia states that objects in _______________________ remain in
_______________________ if not ________________________ forces act on them.
32. Copernicus announced the idea of the moving Earth in the sixteenth century. One of the
arguments against a moving Earth was:
a. Consider a bird sitting at rest in the top of a tall tree
b. The bird sees a worm and drops _____________________, and catches it.
c. It was argued that this would not be possible if earth ____________________ as
Copernicus suggested.
d. The fact that birds do catch worms form high tree branches seemed to be clear evidence
that Earth must be at rest.
33. Objects move with ______________________.
a. You can refute this argument using the idea of ______________________________.
b. Earth moves __________________ km/s, but so do the tree, the worm below, and even
the _______________ in between.
c. Objects on earth move with earth as earth moves around the sun.
d. Earth does not need to be at ______________________ for the bird to catch the worm.
34. Objects move with vehicles
a. If we flip a coin in high-speed car, bus, or plane we can ___________________ the
vertically moving coin as we would if the vehicle were at _____________________.
b. We see evidence for the law of inertia when the ___________________________
motion of the coin before, during, and after the catch is the ___________________.
c. The vertical force of ________________________ affects on the
_______________________ motion of the coin.
d. Flip a coin in an airplane, and it behaves as if the plane were at ____________________.
The coin keeps up with you - _____________________ in action.
35. Concept Check: How does the law of inertia apply to objects in motion?
Self Check
1. If gravity between the sun and earth suddenly vanished, Earth would continue moving in a(N)
a. Curved path
b. Straight-line path
c. Outward spiral path
d. Inward spiral path
2. To say that 1 kg of matter weighs 10 N is to say that 1 kg of matter
a. Will weigh 10 N everywhere
b. Has ten times less volume than 10 kg of matter
c. Has ten times more inertia than 10 kg of matter
d. Is attracted to earth with 10 N of force
e.
3. The Earth moves about 30 km/s relative to the sun. But when you jump upward in front of a
wall, the wall doesn’t slam into you at 30 km/s. A good explanation for why it doesn’t is that
a. The sun’s influence on you is negligible
b. The air in the room is also moving
c. Both you and the wall are moving at the same speed, before, during, and after your
jump
d. The inertia of you and the wall is negligible compared to that of the sun.