ASTR Chap4 hw

Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________

greater than your normal weight at rest

As a giant cloud of gas collapses due to gravity, you would expect its rate of rotation to

increase

According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will

increase by a factor of 4

According to the universal law of gravitation, the force due to gravity is

inversely proportional to the square of the distance between objects.

The amount of gravitational potential energy released as an object falls depends on

its mass and the distance it falls, as well as the rate of gravitational acceleration.

Rapidly moving comets have more ______ energy than slowly moving ones.

kinetic

Tidal forces on Earth are causing

the Earth to slow down its rotation rate

Suppose two objects are attracting each other gravitationally. If you double the distance between them, the strength of their gravitational attraction __________.

decreases by a factor of 4

Suppose that two asteroids are orbiting the Sun on nearly identical orbits, and they happen to pass close enough to each other to have their orbits altered by this gravitational encounter. If one of the asteroids ends up moving to an orbit that is closer to the Sun, what happens to the other asteroid?

It will end up on an orbit that is farther from the Sun.

Fahrenheit

A hot summer day might be 100, Ice cream is stored in freezers at 26

According to what we now know from Newton's laws, which of the following best explains why Kepler's second law is true?

A planet's angular momentum must be conserved as it moves around its orbit.

Which of the following represents a change from potential energy to kinetic energy?

A rock starting from rest on a high cliff, then moving faster and faster as it falls.

Considering Einstein's famous equation, E = mc2, which of the following statements is true?

A small amount of mass can be turned into a large amount of energy.

Suppose that the Sun were to collapse from its current radius of about 700,000 km to a radius of only about 6000 km (about the radius of Earth). What would you expect to happen as a result?

A tremendous amount of gravitational potential energy would be converted into other forms of energy, and the Sun would spin much more rapidly.

Celsius

A typical room temperature is 24, Liquid boils at 100, Water freezes into ice at 0

The fact that the Voyager spacecraft continues to travel out of the solar system, even though its rockets have no fuel, is an example of

Newton's first law of motion.

Earth has two tidal bulges at all times. Approximately where are these bulges located?

One faces the Moon and one faces opposite the Moon.

Einstein's theory, like Newton's, predicts that, in the absence of air resistance, all objects should fall at the same rate regardless of their masses. Consider the following hypothetical experimental results. Which one would indicate a failure of Einstein's theory?

Scientists dropping balls on the Moon find that balls of different mass fall at slightly different rates.

As long as an object is not gaining or losing mass, a net force on the object will cause a change in

velocity

The allowed shapes for orbits under the force of gravity are

ellipses, parabolas, and hyperbolas.

Radiative energy is _________.

energy carried by light

t/f Doubling the distance between two objects halves the gravitational force between them.

false

t/f Process of Science: Gravity only affects very massive objects and we can therefore only test theories about it when looking at the orbits of planets.

false

t/f There is no gravity in space.

false

Newton's Third Law

for any force, there is an equal and opposite reaction force

An asteroid that is moving farther from the Sun is gaining ______ energy.

gravitational potential

Newton's Third Law tells us that

when your are standing, the ground is pushing up on you with a force that precisely balances the downward force of your weight.

In which of the following cases would you feel weightless?

while falling from a roof

Kepler's Third Law explains

why Earth orbits the Sun at a faster average speed than Mars.

Kepler's First Law explains

why Earth's distance from the Sun varies over the course of each year.

Kepler's Second Law of Planetary Motion explains

why Earth's orbital speed varies over the course of each year.

Newton's First Law explains

why a spaceship with no forces acting on it will continue moving even if it has no fuel.

Newton's Second Law explains

why applying a force to a baseball with your arm can cause the baseball to accelerate from rest to the speed at which it leaves your hand.

The video shows a collapsing cloud of interstellar gas, which is held together by the mutual gravitational attraction of all the atoms and molecules that make up the cloud. As the cloud collapses, the overall force of gravity draws the cloud inward __________ because __________.

(Blank 1) gradually becomes stronger (Blank 2) the strength of gravity follows an inverse square law with distance

As the cloud shrinks in size, its central temperature __________ as a result of its __________.

(Blank 1) increases (Blank 2) gravitational potential energy being converted to thermal energy

As the cloud shrinks in size, its rate of rotation __________ because __________.

(Blank 1) speeds up (Blank 2) its total angular momentum is conserved

Which of the following statements correctly state general principles of motion? (Assume that the moving object's mass is not changing.)

-An object that is accelerating is also undergoing a change in momentum. -Accelerated motion includes any motion involving a change in speed, change in direction, or both. -An object that is accelerating is also being acted upon by a (nonzero) net force.

Which of the following are allowed orbital paths under gravity?

1. hyperbolic 2. elliptical 3. parabolic

The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?

30 m/s

Standing on the surface of the Earth you drop a rock down a well and it falls for 5 seconds before hitting the bottom. How fast is it moving when it hits the bottom of the well? Neglect air resistance.

50 m/s

Of the temperature ranges below, which range represents the smallest range of actual temperature?

50-100° Fahrenheit

If your mass is 60 kg on Earth, what would your mass be on the Moon?

60 kg

Choose the correct description of an object that is accelerating?

A car going around a circular track at a steady 100 miles per hour.

If you actually performed and compared the two trials chosen in Part C, you would find that, while the basketball and marble would hit the ground at almost the same time, it would not quite be exact: The basketball would take slightly longer to fall to the ground than the marble. Why?

Because air resistance has a greater effect on the larger ball.

Consider the statement "There's no gravity in space." This statement is:

Completely false

According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?

Earth's orbit would not change.

T/F When energy is converted from one form to another, a tiny amount is inevitably lost.

FALSE

T/F Speed and velocity are the same thing.

False

Suppose you are aboard a rocket that is orbiting Earth in the low, circular orbit shown. If you want to escape from Earth and head to the Moon or Mars along the "escape" path shown, what do you need to do?

Fire the rocket engine in your direction of travel, so that you gain speed.

Newton's 2nd Law of Motion

Force = mass x acceleration

How does the Space Shuttle take off?

Hot gas shoots out from the rocket and, by conservation of momentum, the shuttle moves in the opposite direction.

Why is Newton's version of Kepler's third law so useful to astronomers?

It can be used to determine the masses of many distant objects.

Where does the energy come from that your body uses to keep you alive?

It comes from the foods you eat.

What would happen if the Space Shuttle were launched with a speed greater than Earth's escape velocity?

It would travel away from Earth into the solar system.

We only see one face of the Moon from Earth because

The Moon is already tidally locked to the Earth.

Which of the following examples describes a situation where a car is experiencing a net force?

The car is making a gradual turn.

Kelvin

The coldest possible temperature is 0, Water boils into the gas phase at 373.15

your weight will be greater than normal when the elevator is moving upward with increasing speed. For which of the following other motions would your weight also be greater than your normal weight?

The elevator moves downward while slowing in speed.

When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground. What has happened to the energy?

The energy goes to producing sound and to heating the ground, rock, and surrounding air.

One tidal bulge faces toward the Moon because that is where the gravitational attraction between Earth and the Moon is strongest. Which of the following best explains why there is also a second tidal bulge?

The second tidal bulge arises because gravity weakens with distance, essentially stretching Earth along the Earth-Moon line.

Which of the following statements correctly describes the law of conservation of energy?

The total quantity of energy in the universe never changes.

In considering the Earth-Moon system we find

There are tidal forces on the Moon caused by the Earth There are tidal forces on the Earth caused by the Moon there are tidal forces on the Earth and Moon caused by the Sun, but the Sun's tidal influence is less than the Earth's on the Moon or the Moon's on the Earth.

t/f If an astronaut goes on a space walk outside the Space Station, she will quickly float away from the station unless she has a tether holding her to the station.

This statement is false. She and the Space Station share the same orbit and will stay together unless they are pushed apart.

Which of the following best describes the origin of ocean tides on Earth?

Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth

Which of the following scenarios correctly demonstrates the transformation of mass into energy as given by Einstein's equation, E = mc2?

When hydrogen is fused into helium, whether in the Sun or in a nuclear bomb, the mass difference is turned into energy.

Most people are familiar with the rise and fall of ocean tides. Do tides also affect land?

Yes, though land rises and falls by a much smaller amount than the oceans.

Suppose you are in an elevator car when the elevator cable breaks. Which of the following correctly describes what happens and why.

You float weightlessly within the elevator car because you and the elevator both begin to accelerate downward at the same rate.

Suppose you lived on the Moon. Which of the following would be true?

Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.

Which object has the most kinetic energy?

a 2-ton truck moving 90 km/hr

Kepler's Second Law

a planet moves faster in the part of its orbit nearer the Sun and slower when farther from the Sun, sweeping out equal areas in equal times.

absolute zero

a temperature of 0 kelvins

Newton's 1st Law

an object moves at constant velocity if there is no net force acting upon it.

You have found that tides on Earth are determined primarily by the position of the Moon, with the Sun playing only a secondary role. Why does the Moon play a greater role in causing tides than the Sun?

because the gravitational attraction between Earth and the Moon varies more across Earth than does the gravitational attraction between Earth and the Sun

At which lunar phase(s) are tides least pronounced (e.g., the lowest high tides)?

both first and third quarters

At which lunar phase(s) are tides most pronounced (e.g., the highest high tides)?

both new and full Moons

An apple contains ______ energy that your body can convert into other forms energy.

chemical potential

Gasoline is useful in cars because it has

chemical potential energy

A skater can spin faster by pulling her arms closer to her body or spin slower by spreading her arms out from her body. This is due to

conservation of angular momentum.

Suppose an object is moving in a straight line at 50 miles/hr. According to Newton's first law of motion, the object will

continue to move in the same way until it is acted upon by a force.

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them will

decrease by a factor of 9.

If an object's velocity is doubled, its momentum is

doubled

Which of the following is an example in which you are traveling at constant speed but not at constant velocity?

driving around in a circle at exactly 100 km/hr

Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________.

less than your normal weight at rest

Nuclear fusion in stars converts some of the ______ energy of hydrogen nuclei into light and heat.

mass

The ultimate source of energy that powers the Sun is

mass energy of hydrogen fusing into helium.

Newton's second law of motion tells us that the net force applied to an object equals its

mass times acceleration.

Compared to their values on Earth, on another planet your

mass would be the same but your weight would be different.

Momentum is defined as

mass x velocity

What quantities does angular momentum depend upon?

mass, velocity, and radius

The mass of Jupiter can be calculated by

measuring the orbital period and distance of one of Jupiter's moons.

Kepler's Third Law

more distant planets orbit the Sun at slower average speeds, obeying the precise mathematical relationship p2 =ǎ.

If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be:

one-quarter as strong.

Which of the following is not a conserved quantity?

radiation

The light from Polaris travels through space in the form of ______ energy.

radiative

Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion __________.

the Moon has a larger acceleration than Earth, because it has a smaller mass

What does temperature measure?

the average kinetic energy of particles in a substance

The center of mass of a binary star system is

the balance point of the system, around which the two objects would revolve.

When you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale

In the formula E = mc2, what does E represent?

the mass-energy, or potential energy stored in an object's mass

Kepler's First Law

the orbit of each planet about the Sun is an ellipse with the Sun at one focus.

Due to its much higher density, water heated to 80 degrees (Celsius) contains more ______ energy than air at the same temperature.

thermal

T/F The Moon is slowly moving away from Earth.

true

t/f If you are driving at 30 miles per hour and increase your speed to 60 miles per hour, you quadruple your kinetic energy.

true

t/f The Moon is constantly falling toward Earth.

true

t/f The center of mass for Earth orbiting the Sun lies inside the Sun.

true

Any particular location on Earth experiences __________.

two high tides and two low tides each day