Coffee Filter Parachute Lab: Part 1
Part 1: Explore the concept of terminal velocity with analysis of a falling coffee filter.
Part 2: Compare three parachute designs and make evidence based claims for multiple stakeholders who want specialty parachutes for skydiving, hangliding, and military use.
Background
People use specialized parachutes for different situations. Skydivers, gliders, and the military all use parachutes to slow a fall from extremely high heights, but each of these stakeholders has slightly different needs when it comes to how the parachute slows that fall.
All falling objects (including a human body wearing a parachute) will accelerate until they reach terminal velocity. This terminal velocity is the maximum speed (velocity) achieved by an object as it falls through a fluid (or air in this case). It occurs when the downward force of gravity is equal to the drag force. At the point where the speed of the falling parachutist is no longer increasing, the acceleration has reached zero and the parachuter is said to have reached terminal velocity. For the three parachute uses mentioned above, the desired terminal velocity varies according to the use.
Skydivers: People want to have fun in the air without the parachute, but because most recreational skydivers aren’t trained to land at high rates of speed, the parachute needs to slow them down to a very safe landing velocity.
Hangliding: The point is to hang out in the air as long as possible, enjoying the views! Slow and relaxed is the vibe of this sport.
Military: Soldiers are trying to get to the ground as quickly as possible to avoid detection in the air, while still slowing their fall enough for a safe landing. They are physically trained on how to land, so can handle a bigger impact than those untrained.
Your job is to recommend a specific parachute type to each stakeholder, providing evidence for why that parachute is best for them and their specific needs.
In part 1, you will investigate the motion of a model parachute by looking at data of the drop with a single, unmodified, coffee-filter parachute .
In part 2, you will investigate data for three different parachute prototype models, and make a recommendation to each stakeholder based on evidence.
This dataset and activity contain distance, time and velocity values for a falling coffee filter. Hover on the blue circles with the letter 'i' in the column headers below to see the variables defined. This activity can be used to learn about terminal velocity, acceleration, and motion graphs in the context of a physics or physical science class.
Dataset
A simple model of a parachute (inverted coffee filter) was dropped from a height of 265cm (2.65m). The free Video Physics by Vernier video analysis tool was used to track the location of the falling parachute every 0.3 seconds.
Variables:
Time (s) - This numeric variable is the time elapsed from the parachute release time. Measured in seconds.
Distance (cm) - This numeric variable is the vertical distance of the coffee filter from the ground. Distance = 0 is on the ground. Measured in centimeters.
Velocity (cm/s) - This numeric variable measures how fast the coffee filter is moving towards the ground at a given point. Measured in centimeters per second.
Terminal Velocity? - This categorical variable is meant to record whether or not the parachuter has reached terminal velocity at any given point. The value of “n” = not yet reached terminal velocity and the value of “y” = terminal velocity has been reached.
Activity
Use the Graph tab in DataClassroom to create a distance vs. time graph by showing Distance on the y-axis and Time on the x-axis. You can choose to edit this document by placing your answers in the Doc after making your own copy of it. Click the edit button to the right of this window to get started. Use the camera in the upper right of the graph to copy and paste your graph here:
At what time does it look like the parachute may have reached maximum velocity?
3. What are you looking for on the graph to tell you the parachute is moving at terminal velocity?
4. Now create a velocity vs. time graph by changing your Y-axis to show Velocity. Paste your graph here:
5. Why is the velocity negative? What does it mean for velocity to be increasing but negative?
6. Look at the time you originally estimated as when the parachute reached maximum velocity. Does your velocity graph confirm your prediction, or do you wish to change it? (If you wish to change your answer, what time do you feel more confident about now as the moment where terminal velocity has been reached?
7. What are you looking for on this graph to give evidence for your parachute model moving at terminal velocity?
8. Now add “Terminal Velocity?” on the Z axis. We have simply started the column for you. Go into the data table and make sure that all the data points that you suspect occured before the parachute reached terminal velocity read “n” for no, and from the moment you feel it hits terminal velocity (and all data after) reads “y” for yes.
9. Try adding regression lines and Group by Z (Terminal Velocity?). Use the camera in the upper right of the graph to copy and paste your graph in here.
Do either of the regression lines fit well? Does your terminal velocity regression line fit your prediction for Q6? When looking at real model data (like this is), is your expected slope value close enough or could it be better by changing your point of terminal velocity? Provide evidence for your amount of confidence.
If you change your point of terminal velocity, you can list your new prediction, and provide an explanation for your modification.
