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Find the electric charge required on the earth and moon to balance their gravitational attraction if the charge on the earth is 12.5 times that on the moon.Mass of moon = 6.7 x 10 KMass of earth = 6 x 10 KDistance between moon and earth = 380 KUniversal gravitational constant = 6.7 x 10 N/K

Answer» Using law of gravitations, the force between two point masses is F = M1 = mass of moon = 6.7 x 1022 kg M2 = mass of earth = 6 x 1024 kg r = distance between masses = 380 km G = universal gravitational constant = 6.7 x 10- 11 Nm2/Kg2 Let Q1 and Q2 be the charge on moon and earth respectively. Now the gravitational force must be balanced by the force of repulsion. Q1Q2 = 4pε0M1M2G but Q2 = 12.5Q1 = 12.5 x 4pω0M1M2G ∴ Q2 = 6.11 x 1014 Q2 = 61.11 TC Q1 = 4.89 TC.


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