Speed, Distance, and Time: Experimenting With Acceleration And Velocity

Constant velocity occurs when an object is moving at the same speed and in the same direction; constant acceleration occurs when an object is changing speed at a constant rate. If an object is traveling at an increasing acceleration, its velocity will increase as well. Likewise, if that object is traveling at a decreasing acceleration, its velocity will also be decreasing. An object, however, cannot have both constant acceleration and constant velocity at the same time.

Along with two other members of a group, I conducted a lab experiment about constant acceleration and velocity. In this lab, we rolled a marble across a tabletop and marked the distance it traveled every 0.5 seconds using chalk. We consistently measured this amount of time using a metronome.  We used a flat surface to measure constant velocity, whereas we created a ramp to measure constant acceleration.  The purpose of this lab was to demonstrate the difference between constant velocity and constant acceleration as well as to support our lessons on these traits with data we found ourselves. Our intent was to collect data that we could present as concrete information on a graph.

The markings of the marble’s progressive movements at a constant velocity were equidistant from each other, as expected for an object, which, by definition, is theoretically covering the same amount of distance in a set time interval. Conversely, the markings we made to measure the progress of the marble moving with a constant acceleration grew increasingly further apart from each other as the marble’s journey continued. This is due to the fact that and object moving with a constant acceleration will continue to gain speed at a set rate until its acceleration changes due to the slope of the surface upon which the object moves or until it is acted upon by an outside force. We measured the distance from the starting line of the marble’s trek to each line (each of which were marked 0.5 seconds after the last) and used this information to create x and y points so we could graph our data.

The formula used for constant velocity is V=d/t (velocity is equal to distance over time) and the formula for constant acceleration is d=(1/2)at^2 (distance equals one half of acceleration times time squared).

The graphed line of constant velocity was a straight line whereas constant acceleration formed a slight curve along the graph (we graphed it as a straight line for viewing purposes although the points graphed did not exactly match up with the trend line). The graphs were used to support our data by visually demonstrating the relationship between distance and time in the equations for constant velocity and acceleration. In the velocity graph, distance was shown as values on the y-axis while time was shown along the x-axis. As time increased, distance followed suit, demonstrating a consistently straight line on the graph; this displayed the marble’s constant velocity. In the graph of the marble’s acceleration, distance was again on the y-axis, but the x-axis showed values of time squared as opposed to time. Again, each of these values increased contiguously to show that constant acceleration depended on distance covered in increasingly fast time increments. These graphs supported out demonstrations of the concepts as well as our data collected.

This lab was informative in several ways. I realized in the process of marking of the marble’s movement that more often than not an experiment will need to be repeated for accurate results; in the future I will be prepared for a lab to require time. Things do not always work perfectly on the first try. In future labs I will repeat the careful notation of equations and units as it helped me immensely in my calculations during this experiment. And lastly, I learned from this lab that the experiments we conduct are not simply arbitrary activities- they do in fact relate to our studies of physics and I should work harder in the future to apply my knowledge to the lab as I am conducting the experiment.