The laws of physics govern how long it takes an object to fall to the ground after you drop it. In order to figure out the time, you need to know the distance the object falls, but not the weight of the object, because all objects accelerate at the same rate due to gravity. For example, whether you drop a nickel or a gold brick off the top of the building, both will hit the ground at the same time.
Measure the distance the object will fall in feet with a ruler or measuring tape.
Divide the falling distance by 16. For example, if the object will fall 128 feet, divide 128 by 16 to get 8.
Calculate the square root of the Step 2 result to find the time it takes the object to fall in seconds. In this example, calculate the square root of 8 to find it takes an object to find it takes an object 2.83 seconds to fall 128 feet.