Descriptive Astronomy Ch 3

When we say that a quantity is conserved, we mean that its value does not change. Which of the following are examples of quantities that are conserved for a system of objects?

total momentum,total angular momentum, total energy

Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be__________.

greater than your normal weight at rest

When we say that a planet has a highly eccentric orbit, we mean that:

in some parts of its orbit it is much closer to the Sun than in other parts.

Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law:

Earth travels faster in its orbit around the Sun in January than in July.

According to Newton's second law, the greater the force exerted on an object, the greater the object's _____.

acceleration

Tycho Brahe's contribution to astronomy included:

collecting data that enabled Kepler to discover the laws of planetary motion.

A car is accelerating when it is

going around a circular track at a steady 100 miles per hour.

Compared to their values on Earth, on another planet your

mass would be the same but your weight would be different

According to Kepler's second law, planets and other objects orbiting the Sun move fastest when they are __________.

nearest to the Sun

The time a planet takes to complete one orbit is called its __________.

orbital period

Circumpolar stars are stars that __________.

remain above the horizon at all times

Which person is weightless?

A child in the air as she plays on a trampoline

According to our modern, Sun-centered model, planets rise in the east and set in the west each day because __________.

Earth rotates from west to east each day

Description: Understanding Newton's Version of Kepler's Third Law. Find the orbital period for the planet in each case. (Hint: The calculations for this problem are so simple that you will not need a calculator.) A planet with twice Earth's mass orbiting at a distance of 1 AU from a star with the same mass as the Sun.

1 year

Description: Understanding Newton's Version of Kepler's Third Law. Find the orbital period for the planet in each case. (Hint: The calculations for this problem are so simple that you will not need a calculator.) A planet with the same mass as Earth orbiting at a distance of 1 from a star with four times the Sun's mass.

6 months

Consider the statement "There's no gravity in space." This statement is:

Completely false.

True or False? As you accelerate upward, you have more mass than when you are stationary.

False

Newton's second law of motion states that force equals mass times acceleration or F=ma. Suppose you have already calculated the gravitational force, which we will call Fg,attracting Earth and the Moon. Then the amount of acceleration of Earth due to this force is __________.

Fg divided by the mass of the Earth

Take a sheet of paper and drop it from shoulder height. Then pick it up, crumple it into a ball, and drop it again from the same height. What happens?

The crumpled paper falls to the ground faster.

Suppose two cars both drive for one hour. Which statement is true?

The one that goes faster travels farther

In the Greek geocentric model, the retrograde motion of a planet occurs when:

The planet actually goes backward in its orbit around Earth

If you are in an elevator that is accelerating upward, you will feel __________ while the elevator __________.

a force pressing you to the floor; moves upward with increasing speed

Kepler's third law states that for any planet orbiting the Sun, the orbital period squared ( P2) is equal to the average orbital distance cubed (a3 ), or p2 = a3 . This implies that__________.

a planet with a large average distance from the Sun has a longer orbital period than a planet with a smaller average distance from the Sun

According to Kepler's second law, as a planet or other object moves around its orbit, it sweeps out equal __________ in equal __________.

areas / times

We say that the force of gravity follows an inverse square law with distance. This means that the force attracting two objects _________ as two objects come closer together

becomes stronger

When you are standing on a scale in an elevator, what exactly does the scale measure?

the force you exert on the scale

Compared to its angular momentum when it is farthest from the Sun, Earth's angular momentum when it is nearest to the Sun is

the same.