## Friday, April 8, 2011

### Velocity Lab Investigation

Title: Velocity Lab Investigation

Problem: What is the velocity of a golf ball and ping pong ball, relative to the distance at which they are dropped?

Hypothesis: When the results of the golf ball and ping pong balls are compared, the golf balls will display a larger velocity (in numeric value).

Materials: 1 ping pong ball
1 golf ball
1 meter stick
1 Vernier software (Logger Lite)
1 motion/sonar sensor
A solid, level surface
1 styrofoam cup
1 stopwatch
1 computer

Procedures:
1) Obtain all materials so that the golf and ping pong balls are in the styrofoam cup (so that they don’t move around) for convenience.
2) Hold 1 of the balls right next to the tip of the meter stick, which is held vertically with the ground (solid, level surface).
3) Prepare a stopwatch so that when the ball drops and makes an impact with the ground, the measurements can be calculated accurately.
4) Drop the ball.
5) Stop the watch the second the ball hits the ground, leaving just enough time to catch the ball after the rebound.
6) Record the results of the time (in seconds).
7) Repeat steps 1-7 until a total of 3 tests are documented.
8) Calculate the velocity using the equation d = v * t.
9) Repeat steps 1-8 at a height of 2 meters, then 3 meters.
10) Repeat steps 1-9 for the second ball.
11) Once that is accomplished, assemble the Vernier motion sensor to the computer by plugging it into both the sensor and the interface.
12) It is an option to tape the sensor to the top of the meter stick, however, it is crucial to have a secure bond between the two.
13) Repeat steps 1-10 for both the golf ball and the ping pong ball, but with the motion/sonar sensor (eliminating the stopwatch/human variable).
14) Record all results, take pictures, and make graphs/tables.

Results/Conclusions:
To kick off the results/conclusion section, let’s establish a few facts. According to Newton’s Laws of Motion, the velocity of an object moving by means of gravitational force (Fgrav)- which is calculated to effect all objects with an acceleration of 9.8 m/s/s, or 9.8 m/s^2 (9.8 meters per second squared)- can be measured by dividing the distance at which it is dropped by the time that it takes to reach the bottom (v = d/t). When, in fact, this objects reaches the bottom, it loses acceleration so that it plunges into the negative numbers (in acceleration). Also stated in Newton’s famous scientific regulations (his second Law of Motion, to be exact), that, “the acceleration of an object depends on the force and the mass of the object.” This calculation for force can be described as F = m * a, or force equals mass multiplied by acceleration. This equation can be flip-flopped in any way needed to compute either the force (which is usually referred to as the net force-- a vector quantity produced when two or more forces act upon a single object, whether it be balanced or unbalanced), mass, or acceleration of the object at hand. Mass can be found through the equation: m = F/a (mass equals Force divided by acceleration), and acceleration via a = F/m (acceleration = Force divided by mass). All of the preceding mathematical problems will be useful when examining the results of the Velocity Lab.

Now for the actual experiment. For the first test, my group and I chose the golf ball as our first victim. While the meter stick was held with a stable hand, a second volunteer held the golf ball at the top of the stick, about five inches (horizontal) away from the actual measuring tool. This was prepared in order for the most accurate results, which did not involve the oh-so-rude interruptions from the meter stick. The third participant stood by with a stopwatch in hand and a keen eye for precise timing. This so-called timer had the crucial job of recording the most unambiguous quantifications in order to determine the velocity for later purposes. Each test proceeded in this manner until the third trial was finished at a height of one meter. This was the point at which the average time was determined. (For future knowledge, our main focus was to record the seconds in which it took to travel,or accelerate, towards the floor. This was the unknown needed to be obtained in order to calculate the velocity of each distance.) By adding all of the trials in the one meter row, then dividing the sum by three (the quantity of trials), the average speed was acquired. Once this was accomplished, the triplet tests were repeated at a height of two meters, then three meters. These steps were also repeated for the ping pong ball, whose average times were significantly lower than the golf ball’s, just so that it was made apparent by looking at the sea of lab notebooks. To prove my point, the average heights of the golf ball were: 1.16 s (1 meter), 1.13 s (2 meters), and 1.23 s (3 meters). The opposing ping pong results were of the following: 0.83 s (1 meter), 1.01 s (2 meter), and 1.11 s (3 meters).

As you have probably already experienced on your own, a golf ball has more mass (the amount of matter that is contained inside a body of some sort) than a ping pong ball. This, alone, proves the above hypothesis. However, a second entire set of data was collected using the Vernier motion sensor. The graphs and measurements provided by the advanced software on the computer interface was way beyond the most accurate measurements a human being could record. The below graphs display the velocity, time, and acceleration, all in relation with one another in a visually pleasing manner.
To be perfectly honest, these graphs are very explicit when referring to the numeric values. Nonetheless, the diagrams themselves aren’t exactly the easiest to understand if you don’t have a firm background in physics. One of the variables/sources of the disorganization would have to be that the motion sensor not only recorded motion, but also sound due to its sonar capability. This may have skewed results, but fortunately, they were still distinguishable enough to support the previously stated hypothesis. So to conclude this lab investigation, we could simplify all of the superior information in a single statement indicating that Newton’s second Law of Motion has been proved once again: “the acceleration of an object depends on the force and the mass of that object.”

Golf Ball Test #1 (1 meter)

Golf Ball Test #2 (2 meters)

Golf Ball Test #3 (3 meters)

Ping Pong Ball test #1 (1 meter)

Ping Pong Ball test #2 (2 meters)

Ping Pong Ball test #3 (3 meters)

Isaac Newton