Physical Science-Hewitt Reading Ch. 9

What is the magnitude of the gravitational force between Earth and a 1-kilogram body?

9.8N

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.

Would the spring inside 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?

More compressed going up. Less compressed going down.

What is the Newtonian synthesis?

Newtonian synthesis was the union of terrestrial and cosmic laws brought about by Newton's discovery that Gravity is universal..

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

Newtons law of universal gravitation allowed the mass of the Earth to be calculated.

Distinguish between spring tides and neap tides

Spring tides are when the Earth, Moon and Sun are aligned and the difference between the high and low tides are greater. The neap tides are when the moon is at first or last Quarter (halfway between full moon and new moon). The difference between the high and low tides are less because the pull of the moon and sun partly cancel each other out.

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

The cause of the perturbations of Uranus' orbit was the orbit of the undiscovered planet Neptune. Further observations of the orbits of Uranus and the newly discovered planet Neptune led to the discovery of Pluto in 1930 by Clyde Tombaugh at the Lowell Observatory in Arizona.

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

The gravitational field strength at the surface of a shrinking star increases in a manner that follows the inverse square law. The gravitational field at the surface of a star that has a radius half the size as before will have a gravitational field 4 times as strong at the surface.

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

You weigh more at the bottom of death valley, the distance to the center of the Earth is less than at the top of the mountain. If F = G((m1m2)/d and d is smaller, then the force of gravity. (F) is larger, causing you to weigh more.

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

Your weight is greater than mg if the support force you are on is accelerating upward. Your weight is zero when there is no support force.

Why do both the Sun and the Moon exert a greater gravitational force on one side of the Earth than the other?

because of the distance between the sun or moon and the earth is different for the near and far sides. The near side will feel a greater pull of gravity than the far side.

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 Moon's center of gravity is slightly displaced from it's center of mass. So when the Moon's axis is not aligned, the Earth's gravitational field exerts a torque on the Moon to realign the axis.

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

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

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

every body 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 = m1m2/d2

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

it is 1/4 the thickness of the closer distance. Inversesquare law (1/22 = 1/4 )

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 curving of the path of a planet?

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