How to Measure the Water in a Well by Dropping Stones

For deep wells, it can be difficult to determine the depth of the water because you cannot see the bottom. However, using physics it is possible to calculate the depth of the water because once dropped, the stone will accelerate due to gravity at a rate of 9.8 meters per second squared, and you can determine the distance it traveled by using the distance formula: D = v0*t + 1/2*a*t^2. Since the stone is being dropped, the initial velocity, v0, is zero. In order to calculate the water depth in a well from dropping a stone, you need to know the time it takes for the stone to hit the water and the depth of the well.

Things You'll Need

• Stopwatch
• Rock

Instructions

1. Use the stopwatch to measure the time from when you drop the stone to when you hear the stone hit the water.

2. Calculate the distance traveled by the stone by using the following formula, where T is the time it took for the stone to hit the water:
   Distance = 1/2 * 9.8 * T^2
   For example, if it took 1.5 seconds to hit the water, the stone traveled about 11 meters.

3. Convert the distance traveled from meters to feet by multiplying by 3.28. For example, 11 times 3.28 would be about 36.2 feet.

4. Subtract the distance found in Step 3 from the known depth of the well to find the amount of water in the well. For example, if you know your well is 100 feet deep and the distance from the water to the top is 36.2 feet, the water is 63.8 feet deep.

References

• Basic Physics of Motion
• Physics Equation List