Newtons laws of universal gravitation

[Queen B]

Homework Statement

its 3.8 x 10^8 from Earth's core to the lunar's core
calculate the gravitational attraction exerted by Earth on the moon

Homework Equations

ag = GM/ r^2
G= 6.67 x 10^-11
M of earth= 5.98 x 10^24 ... r= 6.37 x 10^6
M of moon= 7.36 x 10^22 ... r= 1.74 X 10^6

The Attempt at a Solution

ag = ( 6.67 x 10^-11)( 7.36 x 10^22) / ( 6.37 x 10^6) ^2 = 0.12 N
I'm not sure if I'm right or not, I am just really confused as to where I plug in the numbers

 

[Andrew Mason]

Homework Statement

its 3.8 x 10^8 from Earth's core to the lunar's core
calculate the gravitational attraction exerted by Earth on the moon

Homework Equations

ag = GM/ r^2
G= 6.67 x 10^-11
M of earth= 5.98 x 10^24 ... r= 6.37 x 10^6
M of moon= 7.36 x 10^22 ... r= 1.74 X 10^6

The Attempt at a Solution

ag = ( 6.67 x 10^-11)( 7.36 x 10^22) / ( 6.37 x 10^6) ^2 = 0.12 N
I'm not sure if I'm right or not, I am just really confused as to where I plug in the numbers

When the question asks for the gravitational attraction it is asking for the force. You are calculating the acceleration (toward the centre of mass of the earth-moon system). The units would m/sec^2.

Other than that your answer appears to be correct. Welcome to PF by the way!

AM

 

[Queen B]

When the question asks for the gravitational attraction it is asking for the force. You are calculating the acceleration (toward the centre of mass of the earth-moon system). The units would m/sec^2.

Other than that your answer appears to be correct. Welcome to PF by the way!

AM

But how would I calculate the force? And thank you.

 

[SteamKing]

But how would I calculate the force? And thank you.

What is Newton's Second Law of Motion?

 

[Queen B]

F=ma, ok i see now but what mass would i use?

 

[SteamKing]

If you have calculated the acceleration of the moon caused by the earth, then you would use the mass of the ...?

 

[Queen B]

The Earth?

 

[SteamKing]

Try again.

 

[Queen B]

The Moon.

 

[SteamKing]

Good job.