Newtons law of gravitation is F=GMm/r^2, where F is the force between two objects, M and m are the mases of the two objects, G is the universal gravitational constant, and r is the distance between two objects. By knowing information about the size of the earth and making a few measurements, this formula can allow you to determine the mass of the earth. Solve this equation for M

Auniform electric field exists in the region between two oppositely charged plane parallel plates separated by a distance of 1.60 cm . a proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval of 3.20×10-6 s. 1-find the magnitude of the electric field. use 1.60×10-19c for the magnitude of the charge on an electron and 1.67×10-27kg for the mass of a proton 2-find the speed of the proton when it strikes the negatively charged plate