Newtons law of universal gravatational

In summary: So in summary, you need the mass and radius of the moon, and you need the distance between the Earth and moon.
  • #1
daniellelok
11
0
im stuck with this problem:
the question asked for the gravatational force of attraction between moon and Earth while the moon's radius is not given.
do i need the moon's radius? since r is the distance from the center of moon to the center of Earth (right?) and the second question of the same question is that i have to find the Earth's gravitational field at the moon. so if i use GM/r=g, same, moon's radius is not given, so then i cannot calculate it??
my physics sucks a lot, so please help~
 
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  • #2
Well, what are you given? Yes, you will need to know the radius of the moon (you need to know the distance between the center of masses of the moon and the earth). List the values you are given.

In future, please use the homework posting template with which you were provided.
 
  • #3
the given is that the mass of moon and Earth and the radius of Earth and the distance between Earth and moon
 
  • #4
Well, I did a quick search and found that the radius of the moon is 1.738 x 106 m. You can use this in your calculation.
 
  • #5
ok tthx~~ its not in my book tho, I am not sure if the teacher will take that... thanks anyways
 
  • #6
Maybe it's a poorly written problem and whoever wrote the problem neglected to think about adding in the radius of the moon. The moon is pretty small, and actually this distance won't affect your answer much anyway since the radius of the moon is less than 0.5% of the distance from Earth to the moon! So the difference between the answers with and without the radius of the moon is less than 1%.
 
Last edited:
  • #7
Yes, I thought about that gabee.. good idea to just ignore the radius of the moon. For the second question, the radius of the moon is not required, since it asks for the Earth's graviational field strength at the (surface of the) moon.
 

1. What is Newton's law of universal gravitation?

Newton's law of universal gravitation states that every object in the universe attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

2. Who discovered Newton's law of universal gravitation?

Sir Isaac Newton discovered the law of universal gravitation in 1687, published in his famous work "Philosophiæ Naturalis Principia Mathematica".

3. What is the equation for Newton's law of universal gravitation?

The equation for Newton's law of universal gravitation is F = G * (m1 * m2)/r², where F is the force of attraction, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between them.

4. How does Newton's law of universal gravitation explain the motion of planets?

Newton's law of universal gravitation explains the motion of planets by stating that the force of gravity between the planet and the sun keeps the planet in orbit around the sun. The gravitational force decreases as the distance between the two objects increases, which explains why planets move faster when they are closer to the sun and slower when they are farther away.

5. What are some real-life applications of Newton's law of universal gravitation?

Some real-life applications of Newton's law of universal gravitation include satellite orbits, predicting tides and ocean currents, and calculating the weight of objects on different planets. It also plays a crucial role in space exploration and understanding the movement of celestial bodies in the universe.

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