On the line of centres between the Earth and the Moon, there is a point where the net gravitational force is zero. Given that the distance between the two is 385,000 km, and that the Earth has a mass 81x that of the Moon, how far is this point from Earth?

Here, we must consider Newton's Law of Universal Gravitation. This states that the gravitational force acting between two bodies is proportional to the masses of each body and inversely proportional to the square of the distance between them, F=Gm1m2/rAs the Earth is 81 times the mass of the moon, the distance of this point from the moon must be 1/811/2 = 1/9 that of the distance to Earth. This means that we are dealing with a ratio of 1/9 of our distances. We therefore take 385000 * 9/(9+1) to find the distance, which is equal to 346,500 km, or 347,000 km to 3 significant figures.

Answered by Phil R. Physics tutor

5874 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Two balls with the same kinetic energy have mass of ball a = m and ball b = 2m. What is the ratio of their momentums: a/b?


What is the difference between electromotive force and potential difference?


A coil is connected to an analogue centre zero ammeter. A magnet is dropped (North pole first) so that it falls vertically and completely through the coil. What would be observe on the ammeter?


A model truck A of mass 1.2 kg is travelling due west with a speed of 0.90 m/s . A second truck B of mass 4.0 kg is travelling due east towards A with a speed of 0.35 m/s .


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences