Question

A stone is thrown from a cliff and lands in the sea. Air resistance is negligible. Which statement is correct whilst the stone is in motion?
vertical component of stone's displacement is constant
horiz. comp. of stone's displacement is constant
vertical component of stone's velocity is constant
horiz. comp. of stone's veolcity is constant

Answer 1

Since the stone is travelling, the displacement cannot be constant. This leaves the last 2 choices as possibilities. Now consider the acceleration that can act on the stone. Acceleration due to gravity is the only one. That means the horizontal component of the stone has to be constant since there is no acceleration in the horizontal direction.