Week 1 Module 2 HW

A satellite is moved from a low orbit to one that is twice as far from the Earth. Its weight at its new orbit is ____. unchanged decreased by a factor of 2 decreased by a factor of 4 There is no gravity in space. increased by a factor of 2

decreased by a factor of 4

A satellite is moved from a low orbit to one that is twice as far from the Earth. The force of gravity is ____. unchanged decreased by a factor of 2 decreased by a factor of 4 There is no gravity in space. increased by a factor of 2

decreased by a factor of 4

If the distance between two masses is tripled, the gravitational force between them is increased by a factor of 3. increased by a factor of 9. decreased by a factor of 3. decreased by a factor of 9.

decreased by a factor of 9.

Suppose that a planet was discovered that has twice the mass and twice the diameter of the Earth. What would be the escape velocity for this planet? (Assume that for Earth the escape velocity is 11 km/s.) 22 km/s 11 km/s 15.6 km/s 7.8 km/s

11 km/s

The acceleration of gravity on the Earth's surface is 9.8 m/s2. What is the acceleration of gravity at a height of 6,400 km above the Earth's surface? (Hint: recall the 1/r2 dependence and note that the Earth's radius is 6,400 km.) 4.9 m/s2 2.45 m/s2 19.6 m/s2 9.8 m/s2

2.45 m/s2

A 200-kg spacecraft is launched to the Moon. After it has landed on the Moon, its mass is ____. zero 200 kg about 1/6th its weight at Earth The answer depends on which side of the Moon the spacecraft landed on

200 kg

If your mass is 60 kilograms on Earth, what is it on the Moon? 0 kilograms, because the Moon has no gravity 60 kilograms, because mass does not depend on gravity 120 kilograms, because the Moon's gravity is greater than Earth's 360 kilograms, because the Moon is a spherical object

60 kilograms, because mass does not depend on gravity

An astronaut in orbit around the Earth drops her pen, and it floats gently next to her hand. Why does it not fall to the floor? There is no gravity in space. The gravitational pull is very weak at typical altitudes for orbiting spacecraft. Objects in orbit have no mass. All objects in the spacecraft are falling toward the Earth at the same rate. The net force on the pen is zero.

All objects in the spacecraft are falling toward the Earth at the same rate.

A delivery truck and a car collide. Which vehicle experiences the greater force? the truck the car Both the car and the truck experience the same force. We need to know the speed of the truck and the car to find the answer. We need to know the mass of the truck and the car to find the answer.

Both the car and the truck experience the same force.

How can we mathematically express Newton's law of gravity? (In the following, F is the force of Gravity, G is a constant; m and M are the masses or two bodies (such as the Earth and the Sun); and r is the distance between the centers of mass of the two bodies.) F = GMm / r F = GMm / r2 F = GMm / r3 F = Gm2 M / r2

F = GMm / r2

If it were possible to move the Earth so that its new orbit was twice as large as it is now, then the length of a year (in terms of the number of days) would also double. True False

False

If the distance between two objects doubles, the gravitational attraction between them becomes half. True False

False

It is possible to use Newton's modification to Kepler's Third law to determine the mass of Jupiter's moon, Io. True False

False

Newton's laws of motion apply only to objects experiencing the force of gravity. They do not apply to objects experiencing a magnetic force. True False

False

The concept of the epicycle was introduced in the heliocentric model to explain the retrograde motion of the planets. True False

False

The reason the Earth's moon does not fall into the Earth is because it orbits beyond Earth's gravitational pull. True False

False

Kepler's ____ law states that the orbits of planets are elliptical, with the Sun at one focus. First Second Third

First

When a bus makes a sudden stop the passengers lurch forward as a consequence of ____ law. Newton's First Kepler's Third Newton's Third

Newton's First

A magician pulls a tablecloth out from under the settings on a dinner table without disturbing the dishes. This is an example of _________. Newton's First law of motion Newton's Second law of motion Newton's Third law of motion the Hannum-Barnum law Kepler's laws of motion

Newton's First law of motion

rom Kepler's ____ law, we conclude that the planets do not move with constant speed. Second First Third

Second

In Copernicus' model of the solar system, the planets orbited the _____ in ______ orbits. Sun; circular Earth; circular Sun; elliptical

Sun; circular

If the force of gravity exerted on the Sun by the Earth is the same as the force exerted by the Earth on the Sun, why does the Earth orbit the Sun, and not the other way around? The Earth is less massive, and is accelerated more by the gravitational force and moves faster. Planets, by definition, orbit the Sun, and not the other way around. They each orbit around the geometric center of the system. The combined gravitational forces of all the planets keeps the Sun at the center of the Solar System. None of these choices is correct.

The Earth is less massive, and is accelerated more by the gravitational force and moves faster.

How can we tell that the Moon is held in orbit around the Earth by a force? The Moon follows a curved path as it orbits. The Moon's gravity creates tides in the Earth's oceans. The Moon is always the same distance from the Earth. One side of the Moon is always facing the Earth. The Earth's gravitational force pulls inward on the Moon.

The Moon follows a curved path as it orbits.

Why does something weigh less on the Moon than on the Earth? The farther something is from Earth, the lower its weight. The Moon's lower mass creates a lower force of gravity at its surface. The object's weight is the same on the Moon as it is on Earth. The Earth's gravity pulls in the opposite direction as the Moon's, so the net force is reduced. The Moon has no atmosphere to apply a downward force on surface objects.

The Moon's lower mass creates a lower force of gravity at its surface.

Consider an apple falling from a tree. Which of the following apply to this situation? The apple is attracting the Earth. The Earth is attracting the apple. The Earth is attracting the apple; the apple is not attracting the Earth. The Earth is attracting the apple and the Earth is attracting the apple; the apple is not attracting the Earth. The apple is attracting the Earth and the Earth is attracting the apple.

The apple is attracting the Earth and the Earth is attracting the apple.

An astronaut on the Moon drops a feather and a hammer at the same time. Which hits the ground first? The hammer hits first due to its larger mass. The feather hits first due to the decreased weight of the hammer. The feather hits first since there is no air resistance on the Moon. The feather and the hammer hit the ground at the same time.

The feather and the hammer hit the ground at the same time.

A parachutist jumps out of an airplane and opens her parachute. She then floats downward at a constant rate. Why is she not accelerating? The parachute provides an upward force to balance gravity, so the net force is zero. She is accelerating, but gravity's pull is weak at high altitudes. As she falls, she is weightless and therefore cannot accelerate. The parachute has very little mass, so its inertia is negligible. The parachutist exerts a gravitational pull on the Earth that is equal to its pull on her.

The parachute provides an upward force to balance gravity, so the net force is zero.

The surface gravity of Jupiter is only 2.5 times larger than the Earth's, despite the fact that Jupiter's mass is more than 300 times that of the Earth. How can this be? The radius of Jupiter is much larger than the Earth's, so a point in the cloudtops of Jupiter is farther from its center. The radius of Earth is 300 times smaller than the radius of Jupiter. Jupiter is mostly hydrogen and helium, while the Earth is mostly iron and rock. Jupiter has no surface, so it does not have a surface gravity.

The radius of Jupiter is much larger than the Earth's, so a point in the cloudtops of Jupiter is farther from its center.

After tying a string to a rock, you twirl the rock around above your head. If the string were to break, what path would the rock follow? The rock will fall down immediately. The rock will complete the circle before falling down. The rock will go in a straight line before falling down. The rock will fly upward.

The rock will go in a straight line before falling down.

A rocket in space fires its engines continuously until it runs out of fuel. Describe the motion of the rocket. The rocket's speed increases until its engines stop firing, and then coasts in a straight line. The rocket's speed is a constant value until the engines stop firing, and then coasts to a stop. The rocket's speed increases until its engines stop firing, and then coasts to a stop. The rocket's speed does not change, and it continues to move in a straight line. The rocket does not move, as the engines have nothing to push against.

The rocket's speed increases until its engines stop firing, and then coasts in a straight line.

An ion engine provides a small but constant force on a spacecraft as it moves from the Earth to Pluto. Compare the speed of the spacecraft near the beginning of its journey with its speed as it flies past Pluto. The spacecraft's speed at Pluto is the same as its speed near Earth. The spacecraft's speed at Pluto is slower than its speed near Earth. The spacecraft's speed at Pluto is faster than its speed near Earth. The relative speed cannot be determined with the information given.

The spacecraft's speed at Pluto is faster than its speed near Earth.

A planet is discovered at a distance of 1 AU from its parent star with a period of 1 year. How does the star's mass compare to our Sun's? The star has the same mass as the Sun. The star's mass is around 2 times smaller than the Sun's. The star's mass is around 2 times larger than the Sun's. The star's mass is around 4 times smaller than the Sun's. The star's mass is around 4 times larger than the Sun's.

The star has the same mass as the Sun.

A planet is discovered at a distance of 1 AU from its parent star with a period of 2 years. How does the star's mass compare to our Sun's? The star has the same mass as the Sun. The star's mass is around 2 times smaller than the Sun's. The star's mass is around 2 times larger than the Sun's. The star's mass is around 4 times smaller than the Sun's. The star's mass is around 4 times larger than the Sun's.

The star's mass is around 4 times smaller than the Sun's.

Mars completes one orbit around the Sun in approximately two Earth years. Mars' average distance to the Sun is about 1.5 AU. Therefore the Mars' orbital speed is lower than the Earth's orbital speed. True False

True

A car is moving down a straight, steep hill. By applying the brake, the driver is able to keep the speed of the car constant. Which of the following statements is true in this situation? There is a net force on the car. The net acceleration is negative. There is no net force on the car.

There is no net force on the car.

If you see a body in space that is not moving in a straight line at constant speed, what can you say about it? It must be an artificial satellite. There must be a net force acting on it. It is not subject to any outside forces. None of these choices is correct.

There must be a net force acting on it.

An object is moving in a straight line and at a constant speed of 60 kilometers per hour. We therefore conclude that the net force on this object is zero. True False

True

An object moving on a circle at constant speed is an example of accelerated motion. True False

True

Astronomers can determine the mass of the Sun by applying Newton's modification of Kepler's Third law. True False

True

By Newton's Third law, the Earth's pull on the Moon is equal to the Moon's pull on the Earth. True False

True

Copernicus was able to calculate the distances to the observed planets relative to the Earth's distance from the Sun. True False

True

In geocentric theories, the Earth is assumed to be the center of the solar system. True False

True

In the heliocentric model, the retrograde motion of the planets was explained as the consequence of the different orbital speeds of the planets, without the use of epicycles. True False

True

______ major contribution to astronomy is his extensive series of measurements of planetary positions. Tycho Brahe's Galileo's Kepler's

Tycho Brahe's

How are mass and weight different? There is no difference; they are the same. Weight is a measure of how much gravity pulls an object; mass is how much matter the object has. Mass is the amount of matter an object contains; weight is how much mass an object contains. Weight is the amount of matter an object contains; mass is the type of matter an object is made of.

Weight is a measure of how much gravity pulls an object; mass is how much matter the object has.

The Moon is gravitationally attracted to the Earth. Is the Earth gravitationally attracted to the Moon? Yes, but the force of attraction is less. Yes, and the force of attraction is the same. Yes, but the force of attraction is greater. No, the Moon has no gravity.

Yes, and the force of attraction is the same.

The escape velocity from the Moon is 2.4 km/s. If an astronaut hits a golf ball such that it just reaches this speed, the ball will __________________________. continue moving away from the Moon, never to return follow a very elliptical orbit around the Moon move away from the Moon, but return some time later either orbit the Moon or escape its gravitational pull, depending on the direction the ball is hit

continue moving away from the Moon, never to return

A weather satellite moves at a constant orbital speed around the Earth. Is this satellite accelerating? Yes, the satellite is accelerating — its speed is constant but its direction is changing. Yes, the satellite is accelerating — the force of gravity is pulling it toward the ground. Yes, the satellite is accelerating — it is in freefall toward the ground. Yes, the satellite is accelerating — its speed is constant but its direction is changing and Yes, the satellite is accelerating — it is in freefall toward the ground.. Yes, the satellite is accelerating — its speed is constant but its direction is changing, Yes, the satellite is accelerating — the force of gravity is pulling it toward the ground and Yes, the satellite is accelerating — it is in freefall toward the ground. are correct.

Yes, the satellite is accelerating — its speed is constant but its direction is changing, Yes, the satellite is accelerating — the force of gravity is pulling it toward the ground and Yes, the satellite is accelerating — it is in freefall toward the ground. are correct.

If you are lucky enough to get a chance to visit different planets of our Solar System, which of the following statements will be true? Your weight will change, but your mass will remain the same. Your mass will change, but your weight will remain the same. Both your weight and mass will remain the same. Both your weight and mass will change.

Your weight will change, but your mass will remain the same.

Mars completes one orbit around the Sun in approximately two Earth years. Mars orbits at an average distance to the Sun of about 1.5 AU, and Mars' mass is about 1/10 of the Earth's mass. Therefore Mars' orbital speed is _____ the orbital speed of the Earth. about 0.8 times 1.5 times larger than about 1/10 of about 3 times

about 0.8 times

What is the average orbital speed of the Earth around the Sun? (Note: r = 1.5 × 1011 m and P = 3.16 × 107 s .) about 30 km/s about 4.7 km/s about 9.8 m/s2 365 days 1,000 km/s

about 30 km/s

If the net force acting on an object doubles, then the _____ doubles as well. mass acceleration speed velocity

acceleration

Which of the following objects is experiencing the Earth's gravitational force? a boat floating in water an airplane taking-off a skydiver falling under the force of gravity all of these choices are correct Only an airplane taking-off and a skydiver falling under the force of gravity above.

all of these choices are correct

Which of the following objects is obeying Newton's laws of motion? a sleeping cat a satellite orbiting the Earth a runner racing around a track a skydiver falling under the force of gravity all of these choices are correct

all of these choices are correct

At which place on the Earth will you weigh less? at the equator at the North Pole at the South Pole you weigh the same at all of these places

at the equator

If the Moon is suddenly and inexplicably moved to four times its current distance from the Earth, its orbital speed ______________________________________. increases by a factor of 2 increases by a factor of 4 decreases by a factor of 2 decreases by a factor of 4 is unchanged due to its low mass

decreases by a factor of 2

The gravitational force exerted by the Sun on the Earth is ____ the gravitational force exerted by the Earth on the Sun. greater than less than equal to unrelated to

equal to

The speed an object needs to move away from the gravitational pull of the Earth is called orbital velocity. escape velocity. rotational velocity. random velocity.

escape velocity.

The force that pulls an upward going ball back to the Earth and keeps the Moon in its orbit is called _______. inertia gravity pressure escape speed

gravity

What does escape velocity measure? the gravitational attraction at a planet's surface how fast an object needs to go to escape a planet's gravity how far away an object needs to be to escape a planet's gravity how fast an object needs to go to escape hostile space aliens

how fast an object needs to go to escape a planet's gravity

If an object's mass ( M ) is doubled, the gravitational force between it and other objects will be increased by a factor of 2. increased by a factor of 4. decreased by a factor of 2. decreased by a factor of 4.

increased by a factor of 2.

What do we call the tendency of a body at rest to remain at rest or a body in motion to remain in motion? gravity the "action-reaction" law the tendency of a person to stay in bed in the morning inertia

inertia

What property summarizes a body's tendency to stay in the state of rest or motion? temperature acceleration pressure inertia volume

inertia

A diver in mid air is pulled toward the pool below by the force of gravity from the Earth. The Earth experiences an upward force from the diver that ____. is equal to the force on the diver by the Earth is less than the force on the diver by the Earth is greater than the force on the diver by the Earth There is no upward force by the diver on the Earth There is insufficient information to determine the gravitational pull on the Earth by the diver

is equal to the force on the diver by the Earth

The general heliocentric model proposed by Copernicus was appealing, and eventually became preferred, because it was more aesthetically pleasing than the complicated Ptolemaic model. it explained why we do not observe stellar parallax. it replaced the Earth with the Sun as the center of the solar system. it made more accurate predictions than the Ptolemaic model.

it was more aesthetically pleasing than the complicated Ptolemaic model.

Kepler's Third, or harmonic, law states that the semi-major axis of an orbit cubed equals the period squared. period of an orbit cubed equals the semi-major axis squared. planets move fastest when they are closest to the Sun. semi-major axis of an orbit is inversely proportional to the period.

semi-major axis of an orbit cubed equals the period squared.

Galileo's observation of sunspots showed that _________. the Sun was not a flawless sphere the Earth revolved around the Sun planets moved along elliptical orbits around the Sun the stars could change none of these choices is correct

the Sun was not a flawless sphere

In your office, you have a rolling chair and a rolling filing cabinet. The chair weighs 10 pounds, and the filing cabinet weighs 50 pounds (it's partly full). If you push both of them away with about the same strength the chair will accelerate about 25 times as much as the cabinet. the cabinet will accelerate about 25 times as much as the chair. the chair will accelerate about 5 times as much as the cabinet. the cabinet will accelerate about 5 times as much as the chair. both will accelerate about the same.

the chair will accelerate about 5 times as much as the cabinet.

When an astronaut experiences weightlessness in space, their mass is zero. the same as on the Earth. double than on the Earth. becoming lesser and lesser as s/he is going higher.

the same as on the Earth.

Galileo was the first to observe the phases of _____. the venus the moon the earth

the venus

Galileo's observation of the satellites of Jupiter showed that _________. there were objects that did not orbit the Earth planets orbited the Sun the Moon was not a flawless sphere nothing orbited the Earth none of these choices is correct

there were objects that did not orbit the Earth

A satellite is moved from a low orbit to one that is twice as far from the Earth. Its mass at its new orbit is ____. unchanged decreased by a factor of 2 decreased by a factor of 4 There is no gravity in space. increased by a factor of 2

unchanged

A 200-kg spacecraft is launched to the Moon. While in orbit around the Moon, its weight is ____. zero 200 kg about 1/6th its weight at Earth The answer depends on how close to the Moon the ship is orbiting

zero