Key concepts
Physics
Gravity
Drag
Air resistance
Introduction
Have you ever wondered what a parachute and an open rain jacket have in common? They both trap air and slow you down when you move fast! In this activity you will design a parachute for a miniature action figure. Tissue paper or a plastic bag and a few strings are all it takes to make your figure into an expert skydiver.
Background
Things fall because gravity pulls them down—and the faster they fall the harder they land. A lot of people think that heavier objects fall faster. Galileo—a Renaissance philosopher and scientist—showed this idea, although intuitive, is wrong. You can test this idea, too. Drop a small square of cardboard (for example, three by three inches) and piece of paper folded to the same size simultaneously from the same height. Observe that although the paper is lighter than the cardboard, they both reach the ground at the same time. Repeating this with the unfolded sheet of paper will illustrate why parachutes work. The paper falls more slowly when it is in a larger sheet. Why? The explanation is in the air.
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The air around us is made of small particles. Just like you move water particles out of the way when you pass through water, you push air particles out of the way when you move through air. Maybe you have felt how you pushed air out of the way on a bike ride. As you push the air it pushes at you. It slides by you and feels like wind. This is called air resistance, or drag—and it slows you down. You might not like air resistance when you are on your bike but it is ideal when it comes to slowing down a fall! The unfolded sheet of paper fell more slowly than the folded piece of paper because its larger flat surface needed to push more air away. It experienced more drag. Are you wondering how this concept can help you create the best parachute? Try the activity to find out!
Materials
Tissue paper or a plastic bag
Scissors
Ruler
Tape
Hole puncher
Twine
Small, nonbreakable action figure or miniature doll that may be dropped on the floor (If you do not have an action figure, use a piece of clay, a small wooden block, a measuring spoon, etcetera.
Safe location to drop your parachute from—for example, a 2nd-floor window, balcony, open staircase
Preparation
To make the canopy for the parachute, cut a 30- by 30-centimeter square out of the tissue paper (or plastic bag), reinforce the corners with tape and punch a hole in each corner.
Create suspension lines by cutting four strings from the twine, each 30-centimeters long.
To assemble your parachute, attach one end of each suspension line to each corner of the tissue paper, fold the canopy in four so its corners lay on top of one another, and knot the unattached ends of the four suspension lines together.
Procedure
Bring your parachute and action figure to your test location.
In a moment you will drop your figure (without the parachute) from this spot. Do you think it will make a soft or hard landing? Can you predict with precision where it will land?
Drop your figure. Were your predictions correct?
Drop it from the same location several more times. How would you describe these falls?
Attach the parachute to your figure by winding the knotted end of the suspension lines around the middle of your figure and securing it with a knot or tape.
In a moment you will drop your figure equipped with a parachute from this spot. How do you think it will land this time? Can you also predict where it will land?
Fold your canopy in four so its four corners lay on top of one another. Make sure the suspension lines are not tangled. Pick the parachute up from the corner diagonally opposite the corner with the strings. You figure should now hang under the parachute.
Drop your figure equipped with parachute. Were your predictions correct?
Drop it several more times. How are these falls different from the drops without a parachute? Why would a parachute create these differences?
What do you think will happen if you make a hole in the middle of the parachute?
Fold your parachute in four so the corners are stacked. Cut the tip of the corner that is diagonally opposite the corner with the strings attached. Open your parachute and see that there is now a hole in the middle of the canopy. How do you predict this will affect the fall?
Fold your canopy in four again. Pick it up at the corner that has been cut away and drop your figure. Was your prediction correct?
Drop it several more times. How did the hole change the way the figure falls? Why would this happen?
Extra: Investigate how many holes you can create before your parachute no longer functions or whether or not the location of the hole makes a difference. You could also gradually increase the size of the hole and study how its performance changes.
Extra: Make canopies of different materials, sizes and shapes. Which ones work best?
Extra: Measure the impact of the fall by letting your figure land in a sandbox. How deep is the indent created by the fall?
Extra: Use a timer to measure how long the fall takes. Can you calculate the average speed of your figure during the fall? Which parachute creates the slowest fall?
Observations and results
Your figure probably fell straight down and had a hard landing at first. The figure equipped with a parachute probably had a softer landing, but it was probably also harder to predict where exactly it would land. The figure equipped with the parachute with the hole in the middle probably still had a pretty soft landing.
Gravity pulls objects straight down toward the center of Earth. It is strong enough to make falling objects move quickly, creating hard landings! Luckily we have a layer of air around our planet that slows falls. Air resistance or drag pushes against objects when they fall. Parachutes catch a lot of air, creating a lot of drag. They can drastically slow a fall, allowing a softer landing. This slow drop, however, can be hard to control. A figure landing with a parachute might sway to the side during the fall.
Some parachutes trap air, just like a loose jacket can trap air on a bike ride. This trapped air wants to escape. It can often only escape at the edges, which makes those edges (canopy edges or the sides of your jacket) flap. Some parachutes have a hole in the center to release air in a controlled way. It makes the chute more stable, with only a minimal change in drag.
More to explore
Skydiving Science: Does the Size of a Parachute Matter?, from Scientific American
Test Paper Planes with Different Drag, from Scientific American
Showing Science: Watch Objects in Free Fall, from Scientific American
Playtime with Parachutes, from SciShow Kids
Science Activities for All Ages!, from Science Buddies
This activity brought to you in partnership with Science Buddies
