CH 9

What is the magnitude of the gravitational force between earth and a 1 kg body

10 N

What percentage of the universe is presently speculated to be composed of dark matter and dark energy

23% is speculated to be composed of dark matter and 73% of dark energy.

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

6.67*10(-11) N*m2/kg2

What is a gravitational field, and how can its presence be detected

A gravitational field is the influence that a massive body extends into the space around itself, producing a force on another massive body. If you are in the presence of a gravitational field,the gravitational force will pull you towards the object along its gravitational field lines.

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

Anywhere inside a hollow planet the gravitational field of the planet would be zero.

Why is a black hole invisible

Because gravitation is so enormous that the escape of velocity would exceed the speed of light, making a black hole invisible.

When G was first measured by Henry Cavendish, newspapers of the time hailed his experiment as the weighing Earth experiment, why

Because it gives the mass of the entire planet, with all its oceans, mountains, and inner parts yet to be discovered.

Why is there a torque about the moon's center of mass when the moon's long axis is not aligned with earth's gravitational field.

Because the elongated Moon's center of gravity is slightly displaced from its center of mass.

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

Because the pull of the Sun and the Moon work together.

Why do both the sun and the moon exert a greater gravitational force on one side of earth than the other

Because the sun is half effective as the as the moon, the sun pulls 180 times harder on earth than the moon, sun pulls almost as hard on the far side of earth as it does on the near side. The moon's force gets weaker with distance, the gravitational force between the earth & moon is stronger on the side of earth nearer to the moon than on the opposite side of the earth.

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

Everybody attracts every other body with a force that, for any two bodies, is directly proportional to the product of their masses and inversely proportional to the square of the distance separating them. F=mass1*mas2/distance squared

When is your weight equal to mg

For a non-accelerating mass near the surface of Earth.

What do we call the gravitational force between earth and your body

Gravity

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

It would be the same because there is no acceleration.

What did Newton Discover about gravity

Newton discovered the gravity extends beyond earth- that gravity is universal.

Distinguish between spring tides and neap tides

Spring tides are when the Sun, Earth, and Moon are aligned, and the tides due to the Sun and the Moon coincide. This means we have higher than average high tides and lower than average low tides. Neap tides are when the Moon is halfway between new Moon and full Moon, and the tides due to the Sun and the Moon partly cancel each other. Then the high tides are lower than average and the low tides are not as low as average low tides.

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.

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

The gravitational field halfway to the center will be half of the gravitational field at the surface.

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

The magnitude would be zero.

In what sense does the moon fall

The moon falls in the sense that it falls away from the straight line it would follow if there were no forces acting on it.

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

The springs inside a bathroom scale would compress more if I weighed myself in an elevator that accelerates upward. If it accelerated downward then they would compress less.

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

The strength of the gravitational field would become stronger if the star kept shrinking.

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

The thickness of the paint sprayed decreases by ¼.

What is the Newtonian synthesis

The union of terrestrial laws and cosmic laws.

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

The weight is more than mg when it is accelerating upward, and it is zero when it is in free fall.

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

Tides depend more on the strength of gravitational pull.

If Earth shrank with no change in its mass, what would happen to your weight at the surface

Weight would increase.

What was the cause of perturbations discovered in the orbit of the planet Uranus

What greater discovery did this lead to?The perturbations in the orbit of the planet Uranus is the planet of Neptune. This led to the discovery of Pluto.

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

Yes, but earth's tides are much smaller.

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

You are closer to Earth's center at the bottom of Death Valley therefore you weigh more there than at the top peaks of Sierra Nevada.

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

its path along the curved space (due to gravity) around an object instead of gravitational attraction as Newton saw it.