Many of the planets in the solar system have orbits of similar shapes, but they orbit at very different speeds. Why do the planets orbit at different speeds? A. Planets are kept in their orbits by tension force, which is affected by the atmospheric pressure of a planet. B. Planets are kept in their orbits by electromagnetic force, which is affected by the diameter of a planet. C. Planets are kept in their orbits by friction, which is affected by the temperature of a planet. D. Planets are kept in their orbits by gravity, which is affected by the mass of a planet.
D. Planets are kept in their orbits by gravity, which is affected by the mass of a planet. The speed at which a planet orbits is determined by the balance between the gravitational force pulling it towards the Sun and the centripetal force keeping it in orbit. The larger the mass of the planet, the greater the gravitational force and therefore the faster the planet will orbit.
