Why do all planets have different time periods to complete a revolution?

Ans In our solar system, the time taken by each planet to complete an orbit around the Sun varies greatly. Inner planets have much shorter orbits in distance and in time than outer planets. For example, Mercury, the closest planet to the Sun, completes an orbit around the Sun in 88 days while Earth takes one year to make a complete orbit. Pluto, whose average distance from the Sun is about 40 times greater than Earth's, takes 248 years to complete its orbit. In addition, outer planets also take a long time to orbit the Sun because they have slower average orbital speeds than inner planets. Closer to the Sun, the pull of gravity is very strong, so a planet needs a lot of speed to stay in the orbit.