ASTR-100

A satellite is moved from a low orbit to one that is twice as far from the Earth. The force of gravity is ----.

decreased by a factor of 4

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 -----.

decreased by a factor of 4.

If the distance between two masses is tripled, the gravitational force between them is

decreased by a factor of 9.

A 200-kg spacecraft is launched to the Moon. While in orbit around the Moon, its weight is ---.

0

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 11km/s.)

11 km/s

The acceleration of gravity on the Earth'S surface is 9.8 m/ s 2. What is the acceleration of gravity at a height of 6400 km above the Earth's surface? (Hint: recall the 1/r2 dependence and note that the Earth's radius is 6,400 km.)

2.45 m/s2

A 200-kg spacecraft is launched to the Moon. After it has laded on the Moon, its mass is ------.

200kg

If your mass is 60 Kilograms on Earth, what is it on the Moon?

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?

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?

Both the car and the truck experience the same force.

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.

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 /r2

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

False

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

False

When a bus makes a sudden stop the passengers lurch forward as a consequence of law

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

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

Why does something whigh less on the Moon than on the Earth?

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

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.

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 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.

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 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.

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

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 is this situation?

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?

There must be a net force acting on it.

How are mass and weight different?

Weight is a measure of how much gravity pull 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, and the force of attraction is the same.

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 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.

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 pf the Earth .

about 0.8 times

What is the average orbital speed of the Earth around the Sun? (Note: r = 1.5 x 1011m and P =3.16 x 107 s

about 30 km/s

If the net force acting on an object doubles, them the --- doubles as well.

acceleration

Which of the following objects is experiencing the Earth's gravitational force?

all of these choices are correct

Which of the following objects is obeying Newton's laws of motion?

all of these choices are correct.

At which place on the Earth will you weigh less?

at the equator

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 to return

If the Moon is suddenly and inexplicably moved to four times its current distance from the Earth, its orbital speed----.

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.

equal to

The speed an object needs to move away from the gravitational pull of the Earth is called

escape velocity.

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.

false

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

false

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

false

The force that pulls an upward going ball back to the Earth and keeps the Moon in its orbit is called---.

gravity

What does escape velocity measure?

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

What do we call the tendency of a body at rest to remain at rest or a body in motion to remain in motion?

inertia

What property summarizes a body's tendency to stay in the state of rest or motion?

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.

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 5 times as much as the cabinet.

When an astronaut experiences weightlessness in space, their mass is

the same as on the Earth.

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

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

true

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

true

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

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

ture

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