5 ways to say calm down?

The oil is sprinkled on sea waves to calm them down. Why ?

A stone is thrown vertically upwards from the velcity and accleration of the stone (a) on its way (b) on its way down.

A cork of density 0.5gcm^(-3) floats on a calm swimming pool. The fraction of the cork's volume which is under water is

There are 15 trees in a row.4 trees are to be cut down.The number of ways that no two of the cut down trees are consecutive is.