A vector is a mathematical construct that has magnitude and direction. The cross product of two vectors is a binary operation in three-dimensional space that results in a third vector that is ...
In the present situation, both Earth and Mars are moving in the same direction around the Sun, but the slower one, Mars, appears to move backwards compared to the faster one, Earth. Just an illusion. The retrograde motion of Mars â like the apparent motion of the slower car on the highway â is nothing more than an illusion.
In many simple machines, if the load force Fout on the machine is high enough in relation to the input force Fin, the machine will move backwards, with the load force doing work on the input force. So these machines can be used in either direction, with the driving force applied to either input point.