7. Earth has a bad day. It will lead to a brighter future for you though, because it will give us the Moon. Earth is hit by another planet ½ of Earth's diameter (called Theia, the Greek Goddess mother of Selene – The Goddess of the Moon). This really did happen. A) Start with how the Earth-Moon system appears today. Use the data given below, assume that both bodies are uniform spheres and calculate the angular momentum of the Moon due to its rotation, due to its orbital motion and the angular momentum of the Earth due to its rotation. List them from largest to smallest. You may assume that the Moon orbits the center of the Earth.

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Please answer part A and B. show all work please :D

7. Earth has a bad day. It will lead to a brighter future for you though, because it
will give us the Moon. Earth is hit by another planet ½ of Earth's diameter
(called Theia, the Greek Goddess mother of Selene – The Goddess of the Moon).
This really did happen.
A) Start with how the Earth-Moon system appears today. Use the data given below,
assume that both bodies are uniform spheres and calculate the angular momentum of the
Moon due to its rotation, due to its orbital motion and the angular momentum of the Earth
due to its rotation. List them from largest to smallest. You may assume that the Moon
orbits the center of the Earth.
B) Assume that the Earth's day was originally four times longer and its original mass
was 90% of its current mass. Computer models show that to get the right amount of
material into orbit, the impactor had to hit in a grazing collision. Assume that the two
spherical bodies barely touched at impact (this would never happen because the forces
acting on both bodies deformed them a lot – but go with it). How fast must Theia have
been moving on impact?
Useful Information
1. Diameter of Earth: 12756 km.
2. Diameter of the Moon: 3474 km.
3. Mass of Earth: 5.98e24 kg.
4. Mass of the Moon: 1/81 of the Earth.
5. Current orbital period of the Moon: 27.3 days.
6. Average distance from Earth to Moon: 384,000 km.
Transcribed Image Text:7. Earth has a bad day. It will lead to a brighter future for you though, because it will give us the Moon. Earth is hit by another planet ½ of Earth's diameter (called Theia, the Greek Goddess mother of Selene – The Goddess of the Moon). This really did happen. A) Start with how the Earth-Moon system appears today. Use the data given below, assume that both bodies are uniform spheres and calculate the angular momentum of the Moon due to its rotation, due to its orbital motion and the angular momentum of the Earth due to its rotation. List them from largest to smallest. You may assume that the Moon orbits the center of the Earth. B) Assume that the Earth's day was originally four times longer and its original mass was 90% of its current mass. Computer models show that to get the right amount of material into orbit, the impactor had to hit in a grazing collision. Assume that the two spherical bodies barely touched at impact (this would never happen because the forces acting on both bodies deformed them a lot – but go with it). How fast must Theia have been moving on impact? Useful Information 1. Diameter of Earth: 12756 km. 2. Diameter of the Moon: 3474 km. 3. Mass of Earth: 5.98e24 kg. 4. Mass of the Moon: 1/81 of the Earth. 5. Current orbital period of the Moon: 27.3 days. 6. Average distance from Earth to Moon: 384,000 km.
Expert Solution
Step 1

Hello. Since your question has multiple parts, we will solve the first part for you. If you want the remaining part to be solved, then please resubmit the whole question and specify the part you want us to solve.

 

A)

Let DE and DM, and RE and RM denote the diameters and radii of the Earth and the Moon, respectively. Let d denote the distance of the Moon from the Earth.

Let ME and MM denote the masses of the Earth and the Moon, respectively.

Let TM and TE denote the Moon’s rotation period (also its orbital period) and the Earth’s rotation period, respectively.

Let I0M, IM, and IE denote the moments of inertia of the Moon about its rotational axis, that about its revolution axis, and that of the Earth about its rotational axis, respectively.

Step 2

Evaluate the Moon’s rotational angular momentum (L0M) from its rotational angular speed (ω0M) and its rotational period (TM) as follows:

 

L0M=I0Mω0M=25MMRM22πTM=4πME81DM225TM=4π5.98×1024 kg813474 km103 m1 km22527.3 days24 h1 days3600 s1 h=6.83×1028 kg·m2/s

Step 3

Assume that the Moon’s center is at the distance d from the Earth’s center.

First, determine IM by using the parallel axis theorem, and then determine the Moon’s orbital angular momentum (LM) from its orbital angular speed (ωM) and its orbital period (TM) as follows:

 

LM=IMωM=I0+MMd22πTM=2πME8125DM22+d2TM=2π5.98×1024 kg813474 km103 m1 km210+384000 km103 m1 km227.3 days24 h1 days3600 s1 h=2.35×1036 kg·m2/s

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