Final answer:
The force that prevents the planets from floating away is gravitational force.
Step-by-step explanation:
The force that prevents the planets in our solar system from floating away is gravitational force. Gravity, the attractive force between all masses, is what keeps the planets in orbit. Newton's universal law of gravitation relates the gravitational force to mass and distance. Although gravity is the weakest of the four fundamental forces of nature, its attractive nature is what holds us to Earth and causes the planets to orbit the Sun.