Reiew of Universal Law of Gravitation

 $F=\frac{Gmm}{r^2}$  When a satellite is a distance R from the center of Earth, the force due to gravity on the satellite is F. What is the force due to gravity on the satellite when its distance from the center of Earth is 3R?

Force is measured in

A satellite moving in a circular orbit with respect to the Earth's center experiences a gravitiational force. If the satellite is put into a new circular orbit of a smaller radius, how will the gravitational force and the speed of the satellite change, if at all?

Two charges are separated by a certain distance. If each charge and the distance are both doubled, the force on each charge is _____.

Two charged particles held close to each other are released. As they move, the force on each particle decreases. Therefore, the particles have ____.

The net force on a planet is due primarily to the other planets and the Sun. By taking into ccount all the forces acting on a planet, investigators calculated the orbit of each planet. A small discrepancy between the calculated orbit and the observed orbit of the planet Uranus was noted. It appeared that the sum of the forces on Uranus did not equal its mass times its acceleration, unless there was another force on the planet that was not included in the calculation. Assuming that this force was exerted by an unobserved planet, two scientists working independently calculated where this unknown planet must be in order to account for the discrepancy. Astronomers pointed their telescopes in the predicted direction and found the planet we now call Neptune.What fundamental force is the author referring to in this passage as a force between planets?

 $E=\frac{F}{q}$  A charged particle is located in an electric field where the magnitude of the electric fieldstrength is 2.0 × 10^3 newtons per coulomb. If the magnitude of the electrostatic force exerted on the particle is 3.0 × 10^-3 newtons, what is the charge of the particle?