Currently, the weather in much of our country is prohibitive for rocket launching, but several interesting projects can be done that will pique our nation’s fledging scientists’ curiosity and enthusiasm and will have them looking forward to getting outside to test their designs.
In my 30 years of teaching, one of the best indoor projects has been designing, building, and testing parachutes. This can take several days to accomplish and the students will love it. The idea is to build something that can be used later with their water rockets, but designs can be perfected inside where it is warm.
Here’s what it looks like:
On the first day students enter the classroom with materials laid out in lab. The objective of the day, and for the next several days, is to determine which group of students can design and build a parachute that takes the longest to deliver a 50 gram mass to the gym floor from the running track (Why a 50 gram mass? It is the approximate mass of one raw, grade A egg -in other words, the mass of a future egg-o-naut, or what ever works in your school. Note: I suggest that you not use eggs during indoor testing.) Students often test in a nearby stairwell before going to the gym for the recorded drops.
The materials needed are:
- String (We use the smallest yarn size from Walmart)
- Plastic trash bags (the least thickness practicable; note: its nice to know the custodians; keep your room clean, put your chairs on the desks at the end of the day, and have a nice little Christmas gift for them.)
- Masking tape
- Ping pong balls or Plastic Easter Eggs
- A bucket of sand or Play-dough for mass adjustment to 50 grams.
- A stop watch (on your phone).
On a white-board I have a grid pattern for the daily drops for each group in every class. The teacher does the timing and yells out the drop times. The students are responsible for recording their times. Students, when they enter the room after the typically 10 to 15 minute drop session, record their best time of the day on the white board and write down their planned changes for the next day’s drop in their lab report under “hypothesis”. You know the students are curious and enthusiastic when you see them come in to class early, or after school, to check the drop times of their competition.
Remind the kids that their chutes must be deployable from a water rocket when the weather gets warm. (Most chutes are limited to a diameter of approximately 1 meter, but usually less.)
Note: If you think the project is qualitative only, then you are mistaken. Good research usually requires good data collection, and the analysis of the collected data (i.e. mathematics, graphing). Students, when they are competing to create their best designs will quickly see and appreciate the usefulness of data collection and analysis. This is what they do naturally, our job is to get them to do it formally, and see the usefulness of it.
One more note, you of course can adjust the level of the calculations. The necessity of converting to different dimensions (units) is by design.
More about parachutes tomorrow!
A parachute template will soon be available from NERDSinc.!
Example Calculations
- Area of Canopy
- Displacement of Parachute when dropped
- Velocity
- Speed
- Weight of Parachute
- Kinetic Energy
- Gravitational Potential Energy
- Efficiency
Error Analysis
The energy put into your parachute system occurred when you climbed the stairs form the basketball court.
- Calculate Gravitational Potential Energy of your parachute system. The Potential Energy of the parachute system: GPE=mgh
- Calculate the Kinetic Energy of your parachute system. The Kinetic Energy of the parachute system is: KE=1/2mv^2
- The objective of the project is to make the parachute system go as slow as possible. (i.e; minimize the velocity.) We want to calculate the efficiency of the system.
Efficiency of Parachute System =
4. Calculate the Efficiency of each drop.
5. Make a bar graph showing efficiency vs drop for your four drops.