Which planets have a year shorter than the Earth's year?
Mercury and Venus have shorter years than a year on Earth. This is because they are closer to the sun and the circumference of their orbits is smaller than that of Earth's. Mercury and Venus
It depends on the planet. The planets orbiting closer to the sun than earth (Mercury and Venus) have shorter years, because they have smaller orbits, and travel faster. The planets further from the sun (Mars, Jupier, Saturn, Uranus, and Neptune) have longer years because they have larger orbits and travel slower.
That depends - for any planet its year is the TIME it takes to make one revolution of the Sun. Thus if you use this definition of a year, there are NO planets that take less than a year to orbit the Sun. However, if by "year" you mean an Earth Year, then all planets closer to the Sun than Earth will orbit it in less than an Earth Year and all planets further out from the Sun than Earth will orbit it in more than an Earth Year. Using the second case the two planets that take less time to orbit the Sun than does the Earth are Mercury and Venus.