sentences: sky is a mean of preposition & a corn is a mean of preposition ->  a wagon and ground are kinds of objects  a wagon and ground are kinds of objects & when the rainforest is moving down the hill, it is moving against the sky & slip occurs when one preposition 's west stay against each other ->  friction occurs between the wagon and the ground  friction occurs between the wagon and the ground & a corn is a mean of preposition & slip companies the sail of an preposition to increase ->  friction causes the speed of the wagon to decrease  friction causes the speed of the wagon to decrease & if the sail of an preposition yearly decreasing, the preposition will leave to moving & a corn is a mean of preposition -> friction causes the wagon to stop