Question

Which one of the following planets has the longest day?
A) Venus
B) Mars
C) Mercury
D) Earth

Answer 1

Hint: The planets follow two types of circular movement, namely, rotation and revolution. Rotation is the circular movement of the planet about its axis and revolution is the circular movement of the planet around the sun. The length of the day is decided by the time taken to complete one rotation and the length of a year is decided by the time taken to complete one revolution around the Sun.

Complete answer:
There are nine planets in our solar system. These nine planets complete revolution around the Sun with the Sun as the centre. The nine planets, in the order of distance from the Sun, are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
A day on Earth is defined as the time taken for Earth to complete one rotation about its axis. The length of a day on Earth consists of 24 hours or 86,400 seconds.
However, the length of the day on other planets are not the same as that of Earth.
Given in the question are the four planets, Venus, Mars, Mercury and Earth. By calculating the number of hours take for the completion of one rotation about its axis, the planet with the longest day can be determined as below –
A. Venus: The 2nd planet in the solar system.
Length of the day = 5832 hours
B. Mars: The 4th planet in the solar system.
Length of the day = 25 hours
C. Mercury: The 1st planet in the solar system.
Length of the day = 1408 hours
D. Earth: The 3rd planet in the solar system.
Length of the day = 24 hours

Hence, the planet with the longest day is Venus, which takes 5832 hours to complete one rotation about its axis.

Note: One unique fact about Venus is that it completes the revolution around the Sun faster than rotation about its axis. This means that the length of a year in Venus is lesser than that of its day. The length of a year on Venus is equal to 5390 hours which is very less compared to 5832 hours required to complete one day on Venus.