Question

planets are constantly moving. in fact, the name planet means wanderer. what force(s) is responsible for the constant movement of the planets in our solar system? a inertia and gravity b gravity only c inertia only d friction

Explanation:

• Inertia: Planets have a tendency to move in a straight - line path (due to inertia). Inertia is the property of an object to resist changes in its state of motion.
• Gravity: The Sun's gravitational pull acts on the planets. The gravitational force \(F = G\frac{Mm}{r^{2}}\) (where \(G\) is the gravitational constant, \(M\) is the mass of the Sun, \(m\) is the mass of the planet, and \(r\) is the distance between the Sun and the planet) provides the centripetal force required for the planets to move in a curved (elliptical, in the case of planetary orbits) path around the Sun.
• Friction: There is no significant friction in the vacuum of space that would cause or maintain the motion of planets.
• If only gravity acted (option B), the planets would be pulled into the Sun. If only inertia acted (option C), the planets would move in a straight - line path and not be in orbit around the Sun.

Answer:

A. inertia and gravity