A child threw a stone straight down off a high bridge. The initial velocity of the stone was 15.0 m/s (include units and proper significant figures). How fast was the stone moving the instant before it hit the river 3.00 sec later?

The speed of the stone before it hit the river 3.00 sec later. Let v is the velocity at that instant is 45 m/s.

Explanation:

Given that, a child threw a stone straight down off a high bridge.

Initial velocity of the stone, u = 15 m/s

We need to find the speed of the stone before it hit the river 3.00 sec later. Let v is the velocity at that instant. When it come down, it is moving under the action of gravity. Using equation of motion as :

So, the speed of the stone before it hit the river 3.00 sec later. Let v is the velocity at that instant is 45 m/s.