You drop your brand new phone (174 grams) down a well. You hear a splash 8.0 seconds later. What was your phone's speed just before it reached the water? (Hint: you may need to convert units)

v = 232.7 [m/s]

Explanation:

In order to solve this problem we must consider that between the well there is air, so take the speed of the sound of the medium as the speed of the sound in the air, with a value equal to 345 [m/s].

With this value we can calculate the height of the well, by means of the following expression:

v = x / t

where:

v = velocity of the sound [m/s]

x = height of the well [m]

t = time [s]

x = 345*8 = 2760 [m]

Now using the principle of energy conservation we can calculate the potential energy of the phone before it is thrown into the well.

m = 174 [g] = 0.174[kg]

The potential energy is conserved i.e. it will be converted from potential to Kinetics, proportionally. Under this concept we can determine the speed before touching the water in the fall.