Question

Three identical balls are thrown from the top of a building, all with the same initial speed but at different angles. Neglecting air resistance, rank the speeds of the balls at the instant each hits the ground.

Answer 1

The speed of each ball would be same at the instant each hits the ground.

Step-by-step explanation:

From the principle of conservation of energy we know that

PE₁ + KE₁ = PE₂ + PE₂

where PE = mgh

The initial and final potential energies would be same for each ball since all the balls are thrown from the same height.

Now what about KE ?

We know that each ball is thrown with the same initial speed so their initial kinetic energies would be same and in turn their final kinetic energies must be same in order to satisfy th e conservation of energy principle. Therefore, we can conclude that the speed of each ball would be same at the instant they hit the ground. The initial angle of ball doesn't have any impact on the speed of the ball.