# 13-14 physics

Flashcard maker : Lily Taylor
The orbital speed for a satellite orbiting very close to Earth’s surface is
8000 m/s
The reason satellites orbit Earth at least 150 km above the surface is to
be above Earth’s atmosphere
The speed of a satellite in a circular orbit is
constant
The speed of a satellite in an elliptical orbit is
not constant
A period of a satellite is
defined as the time for a satellite to make one complete revolution around Earth
The higher a satellite is,
the less speed is and longer its period is
A circle is a special case of
an ellipse
The circular orbit of a satellite orbiting Earth is characterized by constant
The fastest moving planet in a solar system is
the planet nearest the sun
Pluto takes a longer time to travel around the sun than Earth takes because Pluto
has farther to go and goes slower
An object is placed exactly halfway between Earth and the moon. The object will fall toward
Earth
A projectile is fired vertically from the surface of Earth as 10 km/s. The projectile will
rise and then fall back to Earth’s surface
A vertically oriented rocker that maintains a continuous upward velocity of 8 km/s will
escape Earth
The Earlybird communications satellite hovers over the same point on Earth’s equator indefinitely. This is because
its orbital period is 24 period hours
A satellite near Earth makes a full circle in about an hour and a half. How long would it take a satellite located as far away as the moon to orbit Earth?
Compared to the period of a satellite in orbit close to Earth, the period of a satellite in orbit far from Earth is
longer
Where does a satellite in an elliptical orbit have the greatest kinetic energy?
at the point closest to the planet
Where does a satellite in a circular orbit have the greatest kinetic energy?
anywhere- its kinetic energy is constant
What remains constant for a satellite in an elliptical orbit?
its total energy
Escape speed from the surface of Earth is about
11.2 km/s
The curvature of Earth is such that for every 8000m tangent to the surface, the surface drops about
5 m
Minimal orbital speed about Earth is approximately 8 km/s. Minimal orbital speed about the moon would
less than 8 km/s
When in orbit, a satellite such as the space shuttle is
simply a projectile
If you could throw a baseball horizontally at a speed of 8 km/s and if there were no air drag and nothing to stop it,
it would orbit Earth
As a satellite is moving in orbit around the Earth, the sum of the kinetic energy and potential energy everywhere is
constant
Newton hypothesized that the moon
all of the above
If the mass of Earth increased, with no change in radius, your weight would
increase also
If the radius of Earth decreased, with no change in mass, your weight would
increase
If Earth’s mass decreased to one half its original mass, with no change in radius, then your weight would
decrease to one half your original weight
The gravitational force between two massive spheres
all of the above
A very massive object A and a less massive object B move toward each other under the influence of mutual gravitation. Which force, if either, is greater?
both forces are the same
Two objects move toward each other because of gravitational attraction. As the objects get closer and closer the force between them
increases
Suppose the gravitational force between two massive spheres is 100 N. If the distance between the sphere doubled, what is the force between the masses?
25 N
By noticing that Uranus’s orbit is perturbed and by using the law of gravitation, two astronomers independently discovered
Neptune
The force of gravity on you is greatest when you are standing
on Earth’s surface
The reason the moon does not fall into Earth is that
the moon has a sufficiently large orbital speed
A lunar month is about 28 days. If the moon were closer to Earth than it is now, the lunar month would be
less than 28 days
Each of us weighs a tiny bit less on the ground floor of a skyscraper than we do on the top floor. One reason for this is that
the mass of the building attracts you upward slightly
A planet has half the mass of the Earth and half the radius. Compared to its weight on Earth, an apple on this planet would weigh
twice as much
Consider the gravitational force between Earth and a meteor in outer space. If the meteor moves so its distance from the Earths center doubles, the gravitational force on the meteor will be
one quarter
Which is greater, the gravitational force between Earth and the moon, or the force between Earth and the sun?
Earth-sun
Jupiter has more than 300 times the mass of Earth. Yet on Jupiter’s surface an object only about 3 times as much as it would on Earth. The explanation to this involves Jupiter’s
If you stood atop a ladder on Earth that was as tall as Earth’s radius (so you were twice as far from Earth’s center) your weight atop the ladder would be
one-quarter its normal value
Since Earth is attracted to the sun, why doesn’t it fall into the sun?
Because it has sufficient tangential velocity.
A 560-N woman stands on top of a very tall ladder so she is one Earth radius above Earth’s surface. How much does she weigh?
140 N
Suppose the gravitational force between two masses is 70 N. If the magnitude of one of the masses halves, what is the force between the masses?
35 N
Suppose the gravitational force between two spheres is 70 N. If the distance between the spheres is halved, what is the force between the masses?
280 N
Suppose the gravitational force between two spheres is 30 N. If the magnitude of each mass doubles, what is the force between the masses?
120 N
Compared to the gravitational field on the surface of the Earth, the gravitational field well below the Earths surface is
smaller
The gravitational field strength at the center of the Earth is
zero
If you drop a stone into a hole drilled all the way to the other side of Earth, the stone will
speed up until it gets the center of Earth
If you were to weigh yourself in an elevator that is accelerating upward, compared to your ordinary weight you would weigh
more
If you were to weigh yourself in an elevator that is in free fall, compared to your ordinary weight, you would weigh
zero
There are two main processes going on in the sun that keep the sun in existence. These processes are gravitation and
nuclear fusion
If the sun were to collapse to form a black hole (quite unlikely), Earth would
orbit the black hole just as it orbits the sun now
When a star collapses to form a black hole, its mass
remains the same
If a weight scale shows that you weigh 200 kg on the surface of Earth, and then you skydive with both of your feet attached to the scale, you will read a weight of
0 kg
If you stand on a weight scale in an elevator that is accelerating upwards, why do you observe an increase in your weight?
Because you are accelerating upwards, there is more compression of the springs of the scale. The weight reading on the scale reflects the amount of compression of the springs.
One way that astronauts detect planets around distant stars is by observing to see if there is a _________ in the light that reaches us from a particular star. The reason that the star moves away or toward us is a __________ due to gravitational effects of the planet.
Doppler shift, perturbation
The distance to the center of the Earth is
4000 miles