Motion on an Incline

What’s the Big Idea‽

Motion. On an incline, this time. Not only are we dealing with just one dimension of motion, but two dimensions of motion! In order to understand how linear kinematics work, it is necessary to see what velocity and acceleration look like and how motion in different directions affect each other. (Spoiler: not at all!)

Procedure

For this laboratory, we needed a track, a low-friction cart, a set of physics books, a laptop, and a Vernier LabQuest and a corresponding motion detector. We set up the track with the motion detector at the end, then used the books to elevate the track (that’s really all they’re good for now, since we switched to the iPads). The LabQuest and laptop recorded the data. We placed the cart at the lower end of the track and pushed with moderate force, much like this image suggests:

The push resulted in the cart being pushed up the ramp, until it stopped and rolled back down towards the starting position. The resulting data is as so:

Both graphs are annotated, but I’ll explain them a bit. For reference, each “section” is delineated by yellow lines.The first graph shows position vs. time (i.e. velocity) and the second graph shows velocity vs. time (i.e. acceleration). 

1. In the first section, notice how, on both graphs, the line is different from the rest of the graph. This is the when we were pushing the cart in both the x-direction (when accounting for the ramp angle); it was receiving a net positive acceleration. 
2. The second section shows the cart going up, whereas the third section shows it going down. On the first graph, these to sections make up a quadratic curve; this is gravity doing its work in conjunction with a change in x position (though gravity isn’t acting strictly in the y-direction, in this case). The second graph is also insightful—it’s linear! This is clearly because of gravity’s constant downward force on the cart.
3. The last section shows another little wonky line, like the first section. This is the cart coming into contact with the motion detector.

In addition to the normal procedure of the lab, we played around with the cart, utilizing its spring function. The result was interesting:

For this lab, it doesn’t have that much significance and would most likely be more confusing without additional physics knowledge. But I’m keeping it here regardless of that fact, just because I like it.

Takeaways

There are two main takeaways in the lab. Firstly, the visualization of velocity and acceleration. In different situations, these characteristics of motion look different in real life than they do on a graph. It is important to comprehend graphs in order to get a deeper understanding of physics. Secondly, though I don’t think this lab explicitly dealt with x- and the y-direction motion, I was able to notice the constant acceleration due to gravity, both in the quadratic curve of the first graph and the linear fit of the second graph. Again, this is a vital concept in the comprehension of physics and the world around us.