Physics Chapter 9

What is the magnitude of Earth's gravitational force on a 1-kg body at Earth's surface?

10 N

How many tides are there daily? high and low

2 high and 2 low

It takes the moon _____ hrs and _____ min to orbit the Earth.

24 hrs and 50 min

What is the gravitational constant?

6.67 x 10^ -11 N*kg^2/m^2

What is the magnitude of the gravitational force between two 1-kg bodies that are 1 m apart?

6.67 × 10 -11 N

Reducing the distance between two masses to half while doubling the mass of one of the masses would result in a change of force between the masses of 8x / 2x / no change / ½x / ¼x.

8x

Why are all tides greatest at the time of a full Moon or new Moon?

At full Moon and new Moon, the tides from the Moon and the Sun add because they are in line with Earth.

When is your weight measured as mg?

For a non-accelerating mass near the surface of Earth

The inverse square law formula?

Intensity= 1/distance (or radius) ^2 1/d^2

In what sense does the Moon "fall"?

It falls away from the straight path that it would follow if there were no forces acting on it.

What happens to the strength of the gravitational field at the surface of a star that shrinks?

It increases.

What is a gravitational field, and how can its strength be measured?

It is a force field on any body with mass. Its strength is the force per unit mass on a test mass.

How does the thickness of paint sprayed on a surface change when the sprayer is held twice as far away?

It is ¼ as thick.

If Earth shrank, but there was no change in its mass, then what would happen to your weight at the surface?

It would increase

Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that was accelerating upward? Downward?

More compressed while accelerating upward, but less compressed while accelerating downward

Newton viewed the curving of the path of a planet as being caused by a force acting on the planet. How did Einstein view the curved path of a planet?

Moving in curved 4-dimensional spacetime

What is the units for the gravitational constant?

N*kg^2/m^2

What was the cause of perturbations discovered in the orbit of the planet Uranus? What later discovery did this lead to?

Neptune caused the perturbations, and later Pluto was discovered.

Do the tides rise and fall at the same time each day?

No.

Would a torque on the Moon occur if the Moon were spherical, with both its center of mass and center of gravity in the same location? Why?

No. The torque requires a distance between the center of mass and the center of gravity.

Which has the higher tides: spring tides or neap tides? Why?

Spring tides are higher, because the tides from the Moon and Sun add together.

Who came up with the idea of the Wormhole? and does he believe they exist?

Stephen Hawking but he doesn't believe they exist

Describe how the gravitational forces from the Sun and the Moon compare from one side of Earth to the other

The Sun exerts a stronger force on the side of Earth nearest the Sun, and the Moon exerts a stronger force on the side nearest the Moon.

Why is a black hole invisible?

The escape velocity of the black hole is greater than the speed of light.

How does the force of gravity between two bodies change when the distance between them is doubled?

The force decreases to ¼ of its initial value.

State Newton's law of universal gravitation in words. Then do the same with one equation.

The force is proportional to the product of two masses and inversely proportional to the square of the distance between their centers: F ~ m1m2/d2

Einstein's theory of Gravitation

The gravitational field is a warping of space-time (affects the motion of other objects) by a planet.

What is the Newtonian synthesis?

The union of terrestrial laws and cosmic laws

Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that was moving upward at constant velocity? Downward at constant velocity?

There would be no more compression and no more expansion for both upward and downward motion.

Why are occupants of the International Space Station weightless?

They are in free fall

Do tides depend more on the strength of gravitational pull or on the difference in strengths? Explain.

Tides depend only on the difference.

When G was first measured by Henry Cavendish, newspapers of the time hailed his experiment as the "weighing Earth experiment." Why?

With a known mass, a scale, and the radius of Earth, you can calculate the unknown mass of Earth if you know G

Do tides occur in the molten interior of Earth for the same reason that tides occur in the oceans?

Yes, due to the difference in gravitational force across the core

Where do you weigh more: at the bottom of Death Valley or atop one of the peaks of the Sierra Nevada? Why?

You weigh more in Death Valley because you are closer to the center of Earth.

Give an example of when your weight is greater than mg. Give an example of when your weight is zero.

Your weight is greater than mg when you are accelerating upward. Your weight is zero when you are in free fall.

What is the magnitude of the gravitational field at Earth's center?

Zero N/kg

What would the magnitude of the gravitational field be anywhere inside a hollow, spherical planet?

Zero N/kg

Black hole

a concentration of mass that result from gravitational collapse, near which gravity is so intense that not even light can escape.

Inverse-square law

a law that relates the intensity of an effect to the inverse square of the distance from the cause. Gravity follows this law.

Wormhole

an enormous distortion of space and time.

Gravitational force is always attractive / repulsive. (pick)

attractive

Why do high tides occur every 12 hrs?

b/c the 2 bulges are on opposite sides

Weightless

being without a support force, as in free fall

What did Newton discover about gravity? a) The equation for the force of gravity b) The Newtonian synthesis c) The law of universal gravitation d) All of the above

d) All of the above

Newton's 3rd Law tells us that if a gravitational force exists between two objects, one very massive and one less massive, then the force on the less massive object will be greater than / equal to / less than the force on the more massive object.

equal to

Law of Universal Gravitation

every body in the universe attracts every other body with a force that, for two bodies, is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. F= G m1m2/d^2

The distance between masses is measured from their edges between them / from their centers / from the edge of one to the center of the other.

from their centers

For a planet of uniform density, how would the magnitude of the gravitational field halfway to the center compare with the field at the surface?

g/2 m/s^2

The smaller the distance the ____________ the force.

greater

spring tides

high or low tides that occur when the Sun, Earth and the Moon are all lined up so the tides due to the Sun and the Moon add, making the high tides higher than average and the low tides lower than average.

As the distance between masses decreases, force increases / decreases.

increases

Which has a stronger gravitational pull on the ocean's tides? Moon or Sun

the Moon

Which has a stronger gravitational pull on the Earth? Moon or Sun

the Sun

Weight

the force that an object exerts on a supporting surface usually due to the force o gravity

Gravitational field

the influence that a massive body extends into the space around itself, producing a force on another massive body. It is measured in newtons per kg. (N/kg)

When a star shrinks the mass is concentrated at a ______?

the mass is concentrated at a smaller radius.

Neap tides

tides that occur when the Moon is midway b/w new and full, in either direction. Tides due to the Sun and Moon canceling, making the high tides lower than average and the low tides higher than average.

The greater the distance the __________ the force.

weaker