Building a Plastic Bag Parachute for Gravity Experiments
A homemade parachute made from a plastic bag and a length of string is one of the simplest ways to bring the concept of air resistance to life for primary and lower secondary students. Drop a small mass attached to a canopy and you have an instant demonstration of opposing forces, terminal velocity, and the way shape influences how an object falls. The materials are cheap, the build takes under ten minutes, and the experiment scales up beautifully for a whole class.
Teachers and home educators across Australia often turn to this activity because it ticks the science, maths, and design boxes at once. It also adapts to outdoor spaces such as an undercover courtyard, a verandah, or a balcony, so a wet arvo in Brisbane or a chilly Hobart morning does not stop the investigation. With a bit of planning, the lesson doubles as a low-prep STEM station that runs itself while you float around the room checking predictions.
Gathering Materials from the Classroom and the Servo Run
The classic supply list starts with a light plastic shopping bag, about four lengths of string cut to the same measurement, and a small weight such as a paper clip, a washer, or a stack of Blu Tack rolled into a pellet. Scissors, sticky tape, and a permanent marker complete the kit. Almost every classroom already has these, and what is missing can be sourced from a quick trip to the local Officeworks or a Bunnings hardware run.
For a more polished version, swap the shopping bag for a square of thin plastic from a craft sheet, which gives cleaner folds and a more predictable canopy. Teachers looking to refresh their science trolley will find science and health resources that pair well with hands-on investigations like this one. A small clamp or a binder clip is also handy for attaching the string quickly, especially when younger hands are still mastering knots.
Cutting and Tying the Parachute Canopy
Lay the plastic bag flat on a desk and trim away the handles and the sealed bottom so you are left with a single rectangular sheet. Fold the sheet into a rough square, then snip off any extra so the edges are even. Tie a small loop in the corner of each of the four corners using a simple overhand knot, leaving a tail long enough to thread your string through.
Cut four pieces of string to exactly the same length, around thirty centimetres works well for younger students while older students may prefer longer cords to slow the descent. Thread one length through each corner loop and knot the loose ends together at the bottom. Tie the central knot to your chosen weight and trim any straggly ends so the lines look tidy. A quick test drop from a desk height confirms the strings are even before the real investigation begins.
Setting Up a Drop Test on the Ovals
Take the finished parachute outside to a spot with at least three metres of clear vertical space. A school quadrangle, a covered COLA, or a basketball court works well, and a parent educator at home can use a single-storey verandah or a back pergola. Mark a clear release point at shoulder height using a step ladder or a chair, and lay a sheet of newspaper on the ground so the weight lands in the same spot each time.
Have a student with a stopwatch ready to time the fall from release to landing, and a second student to count aloud. Run three drops with the same design so the class can average the results and talk about why some drops wobble more than others. Swapping the weight between drops gives an instant comparison and prompts questions about mass, drag, and gravity that drive straight into the next lesson.
Comparing Parachute Designs Side by Side
Once one parachute is working, challenge small groups to design a second version with a deliberate change. They might enlarge the canopy, shorten the strings, use a heavier washer, or punch a small hole in the centre of the canopy. Dropping each design from the same height with the same weight turns the playground into a data-collection zone and gives every learner a clear sense of cause and effect.
| Design change | Canopy size | String length | Weight | Approx. fall time |
|---|---|---|---|---|
| Standard build | 30 × 30 cm | 30 cm | 1 washer | 2.1 s |
| Larger canopy | 40 × 40 cm | 30 cm | 1 washer | 3.4 s |
| Longer strings | 30 × 30 cm | 50 cm | 1 washer | 2.6 s |
| Heavier weight | 30 × 30 cm | 30 cm | 3 washers | 1.5 s |
| Hole in centre | 30 × 30 cm | 30 cm | 1 washer | 1.9 s |
A quick class discussion after each round helps students connect the data to the science. Larger canopies catch more air, longer strings give the parachute more time to fill, and extra weight reduces the effect of drag. The hole in the centre lets some air pass through, which is why real-life parachutes sometimes include a vent to stop the canopy from collapsing on impact.
Recording Results and Linking to the Curriculum
The Australian Curriculum asks Year 5 to Year 8 students to investigate how forces act on objects and to use fair testing as a working scientist would. A parachute drop is a fair test in miniature, because only one variable changes at a time while everything else stays the same. Students can record their results in a simple table with columns for design, predicted time, measured time, and a quick sketch of the canopy.
Encourage learners to write a short reflection that names the independent variable, the dependent variable, and the controlled variables. Linking the activity back to gravity, air resistance, and terminal velocity gives the lesson a strong conceptual anchor. A class display of the parachutes themselves, taped above the science bench with the data tables underneath, becomes a permanent reminder of how a plastic bag can turn into a serious piece of scientific equipment.
Extending the Investigation with Light and Plant Growth
Once the gravity experiment has wrapped up, the same cohort of students often has the momentum to tackle a second investigation. Pairing the parachute activity with a plant growth study keeps the materials trolley active and gives the lesson series a connected feel. A guided look at science fair project ideas shows how the same investigative thinking flows from physics into biology.
Ask groups to design a follow-up question such as whether canopy colour affects fall time, or whether string made from different materials behaves differently in humid coastal air. Each prompt extends the original task without adding much prep, and the data tables already in use from the parachute drops transfer across with minor tweaks. By the end of the week the classroom has produced real evidence, real graphs, and a working model that any student can take home to show the family on the weekend.