Question

A raindrop falling from a height h above ground, attains a near terminal velocity when it has fallen through a height (3/4)h. Which of the diagrams shown in figure correctly shows the change in kinetic and potential energy of the drop during its fall up to the ground?

Answer 1

Answer:

B

Explanation:

At height h from ground, the raindrop has a maximum potential energy, with the kinetic velocity as zero

Speed attained after falling through a height = 3h/4

v = √2g×3h/4 = √2gh/2

K.E after falling through a height of 3h/4 = 1/2m×3gh/2 = 2mgh/4

At height h, P.E. = mgh (maximum) and K.E. = 0, thus as raindrop falls, its P.E. decrease and its K.E. increases. Hence during the fall of raindrop first the velocity will increase and then become constant. This constant velocity is called the terminal velocity, hence KE also become constant. PE decreases continuously as the drop is falling continuously. The variation in PE and KE is best represented by figure (b).