Chapter 13: Universal Gravitation
Terms in this set (44)
Legend of Newton's discovery
According to legend, Newton saw an apple fall from a tree and realized that the moon falls toward Earth for the same reason an apple falls from a tree. They are both pulled by Earth's gravity
without an outside force, moving objects continue to move at constant speed in a straight line
The moon falls...
-Around the earth
- The moon falls beneath the straight line it would follow if no force acted on it
-mass does not affect it
The paths of a cannonball fired from the top of a mountain...
-a small horizontal speed would follow a parabolic path and soon hit Earth
- If the speed were faster, the path would be less curved and the cannonball would hit Earth farther away
- At a fast enough speed, the path would become a circle and the cannonball would circle indefinitely
The tangential velocity of Earth
-moves sideways to prevent the moon from hitting the Earth
The moon falls 1.4 millimeters each second (explain)
-An apple falls about 5 m in its first second of fall. The moon is about 60 times farther from the center of Earth than an apple at Earth's surface. The moon should fall 1/(60)2 of 5 m, or 1.4 millimeters in one second
Newton's Theory of Gravitation
-Confirmed the Copernican theory of the solar system
What is the motion of a planet if its tangential velocity were reduced to zero?
-It would crash into the sun
Why are there no large objects in the solar system today with very low tangential velocities?
-They long ago crashed into the sun
Newton's law of universal gravitation
For any pair of objects, each object attracts the other object with a force that is directly proportional to the product of the masses of the objects and inversely proportional to the square of the distance between their centers of mass.
Universal gravitation equation
G: universal gravitational constant
At the top of a mountain your weight...
Is slightly less than at ground level
Inverse Square Law
If one quantity is multiplied by a factor, another quantity decreases by the square of that factor
1, The force is divided by 2.
2. The force is divided by 4.
3. The force is multiplied by 2.
4. The force is multiplied by 4
1. The mass of one object decreases by half
2. The distance between the objects' centers of mass doubles
3. The mass of one object doubles
4. The distance between the objects' centers of mass decreases by half
Where is the gravitational influence of every object is exerted?
Throughout all space
The pulls that Earth and the moon exert on each other is action at a distance because the bodies interact without...
being in contact
-a force field that exists in the space around every massive body
- it interacts with objects by causing them to experience gravitational forces
Gravitational field lines..
-show strength and direction of a force field
-closest together where a field is strongest
-gravitational field is zero at Earth's center
-the weight of a rock at earth's center is zero
Field Lines and Acceleration
related to the acceleration of an object around earth because any mass near Earth will be accelerated in the direction of the field lines at that location
Why are people often unaware that gravity accelerates us?
-because we are almost always in contact with Earth
-Pressure against Earth
-The force you exert against a supporting floor
what is the weight when...
1. sitting still
2. accelerating downward
3. accelerating upward
4. falling freely
1. normal weight
2. less weight than normal
3. greater weight that usual
4. no weight
why will rotating giant wheels likely be used as space habitats in the future?
-Rotation will supply a support force for astronauts, giving them a sense of weight.
How often does high tide occur?
-twice a day
Why is Earth slightly elongated?
The pull of the moon and Earth on each other causes them both to be slightly elongated rather than spherical.
The sun's pull on the Earth
-is 180 times greater than the moon's pull on the earth
- High tides are higher than usual, and low tides are lower than usual
-Occurs at times of a new or full moon.
- Occurs when the sun, Earth, and moon are all lined up.
-The solar and lunar tides coincide.
-Occurs when the moon is halfway between a new moon and a full moon.
-The pulls of the moon and sun are perpendicular to each other.
- The solar and lunar tides do not overlap
A tidal effect causes the solid surface of Earth to...
rise and fall as much as 1/4 meter twice each day
Why do lakes have almost no tides?
There is no significant difference in the moon's pull on different parts of the lake
Gravitation's effects on stars
-tends to crush all solar material towards the center
Nuclear Fusion's effects on stars
-it blows solar material outward
If the fusion rate of the sun increases...
-the sun will get hotter and bigger
If the fusion rate of the sun decreases,
-the sun will get cooler and smaller
Fuel for type of fusion that takes place in the sun
The sun collapse in 5 billion years
-The sun will run out of hydrogen fuel for fusion and gravitation will dominate
-helium will fuse to carbon
-fusion will eventually cause the sun to expand into a red giant
-when the sun no longer gives off heat and light it will be a black dwarf
How black holes form
When extremely massive stars are so massive that they infinitely collapse and its density becomes infinite
-Its gravitational field beyond the original radius of the star is unchanged.
-The configuration of the gravitational field around it represents a collapse of space itself.
- They cause the stars to speed around in tight orbits
How can a black hole be detected?
Matter streams from the visible star of the binary pair toward the black hole, emitting X-rays that can be detected by telescopes.
What role did Gravity play in the formation of our solar system?
A slightly rotating ball of interstellar gas contracted due to mutual gravitation. To conserve angular momentum, the rotational speed of the gas increased, and the particles moved out, producing a disk shape. The greater surface area caused the matter to cool and form clusters that became planets.
Why is Earth Round?
Gravity caused Earth to attract itself together before it became solid. Any "corners" of Earth have been pulled in so that Earth is a giant sphere.
the deviation of an orbiting object from its path around a center of force, caused by the action of an additional center of force
the orbiting body that was discovered in just half an hour because of a perturbation in the orbit of Uranus.
what percent of the universe does each hold:
1. Dark Energy
2. Dark Matter
3. Ordinary Matter