# Measuring the velocity of various objects in freefall

Essay by Anonymous UserCollege, UndergraduateA+, January 1996

Purpose:

The purpose of this experiment was to measure the velocity of various objects in freefall. Upon completion of this lab one will be able to calculate the values for acceleration and the effect of air resistance.

Apparatus:

2m clear plastic tube

Acculab sonic ranger (speed of sound = 343 m/s period = 0.03 seconds)

SensorNet software

Macintosh computer with system 6.07 or later

Blank 3.5 HD Macintosh formatted disk

Electronic mass scale, calipers

Various objects to drop

Procedure

For the first part of Experiment 1 we dropped three objects of the same shape, but of varying mass. To promote accuracy, we performed three trials for each object. The first object we dropped was a 301 gram ball of radius 1.85 cm, followed by a 225 gram ball with radius 1.82 cm, and finally a 20 gram ball of radius 1.81 cm. From this information we were able to derive the mass densities of the objects.

mass density = mass/((4/3)pR3 )

We recorded the relevant data and evaluated the average acceleration by means of the slope of the velocity graph. From the following equation we determined the magnitude of the net force acting on the object:

Force net = mass x acceleration = Force gravity + Force air resistance

Next, we calculated the errors and uncertainties:

mean = 1/N [t1 + t2 + ... + tN] ÃÂº 1/N S ti

s = [1/N S (mean - ti )2]1/2

For the next part of Experiment 1, we simply conducted three trials for a ping pong ball of mass 20 grams and radius 1.81 cm. We followed the same basic procedure as above. Upon completion of three trials, we compared the data collected for the light object with that of a heavy object.

The method used in Experiment 2 is a lot...