Transcript ch 4 sect 2 PP part 1

Chapter 4 Section 2
Part 1 of 2
Define Gravity:
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Define Gravity:
Gravity is an attractive force between any two objects that
depends on the masses of the objects and the distance
between them.
Gravity is one of four basic forces. What are the other three?
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Gravity is one of four basic forces. What are the other three?
Electromagnetic
Strong Nuclear
Weak Nuclear
Isaac Newton formulated the law of universal
gravitation, which he published in 1687.
This law can be written as the following equation:
Isaac Newton formulated the law of universal
gravitation, which he published in 1687.
This law can be written as the following equation:
In this equation G is a constant called the universal gravitational constant, and
d is the distance between the two masses, m1 and m2.
Lets look at some examples for F=Gm1m2:
d2
9.8m (3kg) (2kg) = 14.7N
s2
(2m)2
Reduce the distance:
9.8m (3kg) (2kg)
s2
(1m)2
= 58.8N
Reduce the mass:
9.8m (1kg) (2kg)
s2
(2m)2
= 4.9N
According to the law of universal gravitation, the
gravitational force between two masses ___________
rapidly as the distance between the masses __________
No matter how far apart two objects are, the gravitational
force between them never completely goes to zero.
According to the law of universal gravitation, the
gravitational force between two masses decreases
rapidly as the distance between the masses increases.
No matter how far apart two objects are, the gravitational
force between them never completely goes to zero.
In the 1840s the most distant planet
known was Uranus. The motion of
Uranus calculated from the law of
universal gravitation disagreed slightly
with its observed motion. Some
astronomers suggested that there must be
an undiscovered planet affecting the
motion of Uranus.
What was the name of this planet?
In the 1840s the most distant planet
known was Uranus. The motion of
Uranus calculated from the law of
universal gravitation disagreed slightly
with its observed motion. Some
astronomers suggested that there must be
an undiscovered planet affecting the
motion of Uranus.
What was the name of this planet?
As a result of these calculations, the
planet Neptune was found in 1846.
What is it when all forces except gravity
acting on a falling object can be ignored?
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The acceleration of a falling object in free
fall is about ________ given the symbol g
and is sometimes called the
_______________________________
By Newton’s second law of motion, the force
of Earth’s gravity on a falling object is the
object’s mass times the acceleration of gravity.
We call this _______________________
What is it when all forces except gravity
acting on a falling object can be ignored?
Free fall
The acceleration of a falling object in free
fall is about 9.8 m/s2 given the symbol g and
is sometimes called the acceleration of
gravity.
By Newton’s second law of motion, the force
of Earth’s gravity on a falling object is the
object’s mass times the acceleration of gravity.
We call this weight.
If a 10 kg object falls from the Empire State Building,
what is the gravitational force on the object?
HINT remember G is an acceleration so you have F and A Use F=MA
If a 10 kg object falls from the Empire State Building,
what is the gravitational force on the object?
HINT remember G is an acceleration so you have F and A Use F=MA
What we know:
M= 10kg
A= 9.8 m
s2
Use the formula:
(10kg)(9.8m/s2)=98kg m/s2
Which we know is 98N
What equation would we use to find weight?
What equation would we use to find weight?
Weight and mass are not the same describe each.
Weight is __________________________________
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Mass is ___________________________________
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Example:
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Weight and mass are not the same describe each.
Weight is a force (the gravitational pull) based on how
much mass an object has.
Mass is how much matter is packed into an area.
Example: More marbles more “stuff” more mass;
which then leads to more gravitational pull or weight.
The weight of an object can change, depending on the
gravitational force on the object.
The table shows how various weights on Earth would be
different on the Moon and some of the planets.