Download Directions: Correct the following Myths and Other Misconceptions

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Unit 4 GRAVITY – Homework Packet # 2
PART 1: EUREKA
Gravity
1. The story so far …
Force depends both upon ______________________________ and upon ____________
__________________________________.
Since acceleration refers to ___________________________ and since speed can be
measured in ____________________________ , acceleration is measured in ____________
___________________________.
2.
Who was puzzled by things falling down?
3.
What’s happening in the tug of war between the earth and the stem?
4.
What force is pulling everything down?
5. What did Newton realize?
6.
Why does it seem like all things are attracted to the earth?
7. What is happening when the apple, the acrobat, the picture, and so on fall?
8. How much force was there trying to pull the apple from the tree?
9. What is the approximate rate of acceleration at which things fall?
10. What must you be doing when you hold the apple?
11. What do we call this force needed?
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PART 2 - Cartoon Guide to Physics: Gravity Section
Answer the questions below as you read through the Cartoon Guide to Physics about Gravity.
1. The moon is in uniform circular motion. This means the moon moves in a circular path at a
constant speed. However, we say the moon is accelerating. Why?
2. If there were no gravity, what would be the path of the moon? Why?
3. What do we mean when we say the moon is falling?
4. Why does an apple fall further than the moon?
5. What are 2 ways to increase the gravitational force between two objects?
6. Why isn’t gravitational attraction felt between two people?
7. Draw and label a picture to show the formation of high/low tides.
8. What are three ways to decrease your weight?
9. What are the differences between mass and weight?
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10. What’s the equation that shows the relationship between mass and weight? What does each letter
stand for?
11. What are the four basic forces in physics? Which one do you feel?
12. Why don’t you feel gravity?
PART 3 – EXPLORING GRAVITY
Pretest Quiz: Answer these questions with your prior knowledge about gravity.
1. How would you define gravity?
2. The terms weight and mass are often used to mean the same thing. However, they
are different. Give a definition for each term.
3. Would a feather and hammer dropped on the moon land at the same time? Why?
4. Would a feather and hammer dropped on the earth land at the same time? Why?
5. How does weightlessness affect astronauts living in space?
Post Test Quiz: After viewing the movie answer the following questions. You may use
your book to help.
1. Most textbooks and dictionaries define gravity as the pull towards the center of the Earth. Give a
better definition.
2. Weight and mass are not the same thing. Tell how they are different by supplying a definition for
each.
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3. Mass is measured with a balance beam. If we mass an object on Earth and then take the object and
balance beam to the moon, the mass would be the same. Why?
4. Astronauts on the moon can bounce around easily. They can jump higher than they could on Earth.
Why?
5. Why are stars, planets, and moons round?
6. On the moon, a hammer and feather released at the same height and at the same time will land at
the same instant. Why doesn't that happen on Earth?
7. Give a definition for the term vacuum.
8. What factors determine the amount of gravitational attraction between two
objects?
9. What is a black hole?
PART 4 - What Are Your Ideas About Gravity?
Use your knowledge of gravity to answer and explain the following scenarios.
1. Which object will hit the ground first in
2. Why is the Earth round?
each picture to the right: an apple or a
feather? Why?
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3. Which end of the axe will hit the ground first if dropped?
4. This drawing shows an enlarged person holding a rock.
a. If he threw the rock slightly to his right, what path would the rock take? Show
what happens to the rock by drawing a line showing the complete path of the
rock, from the person's hand to where it finally stops.
b. Why will the rock fall that way?
c. What path would the rock take if the person threw it a little harder?
5. With enough force, would it be possible for the rock never to hit the Earth?
Draw the path of a rock that never hits the Earth.
Directions: Correct the following Myths and Other Misconceptions about gravity. Explain why each is
wrong.
1. Gravity is down.
2. Weightlessness is because one is in space and space doesn’t have gravity.
3. Black holes suck everything into them.
4. Heavier objects fall faster!
5. Astronauts on the Moon were weightless!
6. Tides are because of a full moon and they make people act weird.
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Part 5: Inverse – Square Law
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PART 6: GRAVITATIONAL FORCE
GFORCE=G m1
x
m2
G = 6.67 x 10-11 m3/kg-s2
(d)2
Example:
10 m
10 kg
GF
10 kg
10 kg x 10 kg = 100 = 1 unit of force
(10 m)2
100
Calculate how many units of force there are between the following objects.
10 m
F=
20 kg
10 kg
10 m
20 kg
20 kg
F=
5m
10 kg
10 kg
F=
20 m
10 kg
10 kg
F=
20 m
20 kg
20 kg
F=
30 m
10 kg
10 kg
40 m
10 kg
F=
10 kg
F=
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PART 7 - Universal Law of Gravitation Practice Problems
Use the ULoG to answer the questions below.
1. Suppose that two objects attract each other with a gravitational force of 16 units. If the distance
between the two objects is doubled, what is the new force of attraction between the two objects?
2. Suppose that two objects attract each other with a gravitational force of 16 units. If the distance
between the two objects is reduced in half, then what is the new force of attraction between the two
objects?
3. Suppose that two objects attract each other with a gravitational force of 16 units. If the mass of both
objects was doubled, and if the distance between the objects remained the same, then what would be
the new force of attraction between the two objects?
4. Suppose that two objects attract each other with a gravitational force of 16 units. If the mass of both
objects was doubled, and if the distance between the objects was doubled, then what would be the
new force of attraction between the two objects?
5. Suppose that two objects attract each other with a gravitational force of 16 units. If the mass of both
objects was tripled, and if the distance between the objects was doubled, then what would be the new
force of attraction between the two objects?
6. Suppose that two objects attract each other with a gravitational force of 16 units. If the mass of
object 1 was doubled, and if the distance between the objects was tripled, then what would be the
new force of attraction between the two objects?
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Critical Thinking
Apply the ULoG to the situations below.
7. Having recently completed his first Physics course, Noah Formula has devised a new business plan
based on his teacher's Physics for Better Living theme. Noah learned that objects weigh different
amounts at different distances from Earth's center. His plan involves buying gold by the weight at one
altitude and then selling it at another altitude at the same price per weight. Should Noah buy at a high
altitude and sell at a low altitude or vice versa?
8. Anita Diet is very concerned about her weight but seldom does anything about it. After learning
about Newton's law of universal gravitation in Physics class, she becomes all concerned about the
possible affect of a change in Earth's mass upon her weight. During a (rare) free moment at the lunch
table, she speaks up "How would my weight change if the mass of the Earth increased by 10%?" How
would you answer Anita?
9. When comparing mass and size data for the planets Earth and Jupiter, it is observed that Jupiter is
about 300 times more massive than Earth. One might quickly conclude that an object on the surface of
Jupiter would weigh 300 times more than on the surface of the Earth. For instance, one might expect a
person who weights 500 N on Earth would weigh 150000 N on the surface of Jupiter. Yet this is not
the case. In fact, a 500-N person on Earth weighs about 150 N on the surface of Jupiter. Explain how
this can be.
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