The gravitational force of a star on an orbiting planet 1 is f1. planet 2, which is twice as massive as planet 1 and orbits at three times larger distance from the star, experiences gravitational force f2.
what is the ratio f2f1? you can ignore the gravitational force between the two planets.

Why do scientists believe that light is made of streams of particles? scientists believe that light is made of streams of particles because only the presence of photons can explain phenomena observed during experiments on the photoelectric effect. these observations include only some frequencies of light causing the ejection of electrons, no time gap existing between light striking a metal and electrons being ejected, and intensity having no effect on the kinetic energy of the ejected electrons.

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

How are calculation for velocity and speed different