The speed at which any planet moves through space is constantly changing. in a perfectly circular orbit, the orbital radius of the planet would be constant and therefore so would be its observed angular velocity. in elliptical orbits, the angular velocity varies. in elliptical orbits, the orbital radius of the satellite will vary and therefore so will its angular velocity. the planet travels "faster" (greater angular velocity) when closer to the sun, then "slower" (less angular velocity) at a more distant radius. according to newton's 2nd law, what is the underlying force behind this change in velocity? a) mass b) gravity c) friction d) projectile motion