Parachute Plummet
Make a parachute using simple materials and watch how the forces of gravity and air resistance affect it as it falls.
- One single-ply square paper napkin roughly 10 inches by 10 inches (25 cm by 25 cm); you can also separate double-ply napkins
- Four 10-inch (25-cm) pieces of lightweight string
- Five adhesive dots or pieces of tape
- One jumbo paper clip
- Optional: different types of string, such as yarn, cotton string, or ribbon; different types of material for the canopy, such as fabric, tissue paper, newspaper, or plastic bags; different kinds of weights, such as washers
- Using a sticky dot or piece of tape, secure a string to each corner of the napkin (click to enlarge the photo below).
- Twist the free ends of the four strings together (click to enlarge the photo below).
- Fold up the twisted ends of the strings to form a loop (click to enlarge the photo below).
- Secure the loop with a sticky dot or piece of tape (click to enlarge the photo below).
- Hook the paper clip through the loop (click to enlarge the photo below).
Take your assembled parachute to a safe, elevated launching location, such as a flight of stairs or a balcony. Then, to launch your parachute, pinch the top in the middle of the canopy (see photo below), hold it up, and release it!
Watch your parachute carefully as it falls. Notice how it falls quickly at first, then slows to a steady rate. What else do you notice about how your parachute moves?
Even though we can’t see it, air is made of matter and will push back against an object moving through it. The force of air against an object is called air resistance, or drag. The faster an object goes, the greater the drag, since more air molecules are getting pushed out of the way.
The main forces acting on a parachute are gravity and drag. When you first release the parachute, the force of gravity pulls it downward, and the parachute speeds toward the ground. The faster the parachute falls, though, the more drag it creates. The drag force resists the downward movement of gravity, pushing the parachute back up.
As the parachute falls, the drag increases until it just balances out the pull of gravity. At that point, the parachute stops speeding up, and begins to fall at a steady speed. This steady speed is known as terminal velocity, the fastest something will go when pulled on by gravity in the presence of air resistance.
Can you slow the fall of your parachute even more? See if changing parts of your parachute makes it fall more slowly. Try changing the type or length of string you secure to your parachute. Try a new material for the parachute canopy, or change its shape or size. Try adding more weight to your parachute.
Watch your new parachutes as they fall. How do you think the changes you make affect the parachute’s motion?
Encourage learners to engage in science practices by raising questions about why their parachutes move in particular ways, or how they could change their parachutes to make them work better. They can then plan and carry out investigations to answer these questions. You may have to help learners collect, analyze, and interpret their data in order to figure out the answers to their questions.
