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Laabri

4.04 Kepler Lab MOD 25-26

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Last updated about 1 month ago
9 Nsɛmmisa
Hyɛ no nsow a efi ɔkyerɛwfo no hɔ:

If you need help, please watch the class recording

Please note that this recording uses the regular version of the lab.

If you need help, please watch the class recording

Please note that this recording uses the regular version of the lab.

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Asemmisa {{asɛmmisaAhyɛnsode}}
1.

Part 1: First Law

Kepler’s first law states that an orbit is in the shape of a slightly flattened circle, or ellipse. While a circle contains a single point at its center, an ellipse contains two critical points, called foci (singular: focus). The Sun is located at one focus of a planet’s orbit.

Observe the orbits of the inner planets around the Sun. Mercury's orbit is in red.

What do you notice about Mercury's orbit?

Is Mercury always the same distance from the sun?

Asemmisa {{asɛmmisaAhyɛnsode}}
2.

The eccentricity of an ellipse describes how “flattened” it is.

A circle has an eccentricity of 0.

A flat line segment has an eccentricity of 1.

In the image above, when eccentricity = 0.01, the ellipse is almost a perfect circle. The closer the eccentricity gets to 1, the more flattened the ellipse becomes.

Examine the eccentricity of each planet's orbit.

Eccentricity

Mercury 0.206

Venus 0.007

Earth 0.093

Mars 0.048

Jupiter 0.054

Saturn 0.046

Uranus 0.046

Neptune 0.01

Pluto 0.248

Which has the least eccentric (most circular) orbit?

Asemmisa {{asɛmmisaAhyɛnsode}}
3.

Part 2: Second Law

Observe Mercury's orbit played at different speeds:

What do you notice about Mercury's speed as it orbits the Sun?

Asemmisa {{asɛmmisaAhyɛnsode}}
4.

Kepler’s second law states that a planet speeds up as it gets closer to the Sun, and slows down as it moves farther away.

Observe Pluto (orbit in red). Does Pluto follow Kepler’s second law?

Asemmisa {{asɛmmisaAhyɛnsode}}
5.

The image below shows Pluto in its counterclockwise orbit around the Sun. Pluto's orbit is highlighted in red. Which of the following statements is true?

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6.

Part 3: Third Law

Kepler’s third law describes the relationship between a planet’s orbital radius, or its average distance from the Sun, and the planet’s period, or amount of time to complete an orbit.

How do you think the period of a planet will change as its distance from the Sun increases?

Asemmisa {{asɛmmisaAhyɛnsode}}
7.

Orbital radius (distance from the Sun) is measured in Astronomical Units (AU).

1 AU = the distance from the Earth to the Sun

Period is measured in Earth years. 1 Earth year = 365 Earth days

Orbital radius (AU) Period (Earth years)

Mercury 0.387 0.24

Venus 0.723 0.62

Earth 1 1

Mars 1.52 1.88

Jupiter 5.2 11.86

Saturn 9.55 29.46

Uranus 19.2 84.01

Neptune 30.1 164.79

Pluto 39.529 248.54

What happens to the period as the orbital radius increases?

As the orbital radius increases, the period

Asemmisa {{asɛmmisaAhyɛnsode}}
9.

Summarize Kepler's Laws.

Draggable itemarrow_right_altCorresponding Item

3rd Law (Law of Harmonies)

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Planets orbit the Sun in ellipses with the Sun at one focus.

1st Law (Law of Ellipses)

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A planet sweeps out equal areas in equal times, so it moves faster when it’s nearer the Sun and slower when it’s farther away.

2nd Law (Law of Equal Areas)

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A planet’s orbital period is proportional to its average distance from the Sun (so farther planets take much longer to orbit).