Overview
Launch the Graphical GW app downloaded and prepare to collect acceleration data.
Pre-Lab
1.Imagine that you are going to quickly push the device away from your body while the table. Draw a free body diagram showing the horizontal forces acting on the device as it accelerates as a consequence of the push.
2.Imagine that you are going to quickly push the device forward away from your body. What would be the momentum of the device prior to the push? After it comes to a complete stop? Is there a net change in momentum?
Lab
For this lab, I am going to ask that you slide your device across a slick surface. If you have a grippy case on your device you might need to put it on top of a sheet of paper.
To do this:
Place the device so that it is flat on the table in portrait and you can see the Vernier Graphical GW app
Touch the “Collect”
While watching only the y-data , QUICKLY push the device forward and release it.
You want to push it so that it goes as straight as possible.
You also want to push it so that it slides to a stop with your hand off of the device. You shouldn’t be pushing it the whole time
Once the phone stops, stop collecting.
3.Sketch below what the graph of the y-data looks like during the push and slide to stop. (You might have to do this multiple times).
4.What forces account for the positive and negative accelerations observed on the graph?
5.Your acceleration data is an approximation of what the force data would look like. Look at the areas under your curve. In terms of the impulse-momentum relationship, do the areas make sense? Why do you say so? Your answer should note whether or not you think there was a net impulse and a change in momentum over the course of the motion.
Consider the questions you just answered for pushing the device. Now, you are going to do something similar for standing up from a chair. Think about the forces involved, the vertical velocity of the person at the start and at the end of standing up, and what the impulse profile might look like.
6.Make a free body diagram showing the vertical forces acting on the body as you are standing up from a chair. (Assume the body has JUST LEFT CONTACT with the chair.)
7.In the space below, draw a graph of what you think the vertical acceleration of the body’s COM will look like over time while standing up. Label on your graph what forces you think are contributing to any positive or negative accelerations you have drawn.
Your task is to stand from a seated position while starting and then pause the data collection. It might be helpful to read the instructions before continuing. In a seated position, hold your device upright and as close to the body as possible, touch the “Start” button, stand up, and touch the “Stop” button.
8. Sketch what the data look like and label on your graph what forces you think are contributing to any positive or negative accelerations you have drawn.
9.Your acceleration data is an approximation of what the force data would look like. Look at the areas under the curve. In terms of the impulse-momentum relationship, did the data you recorded when standing up make sense? Why or why not?