Turn your sound on, then press play.
Drop a paper cup and it hits the floor in less than a second. Add a parachute and the same cup drifts down slowly. Two forces explain the difference.
Gravity is the force that pulls everything toward the ground. The moment you let go of the cup, gravity starts pulling it down, and the cup falls faster and faster.
Air is real stuff. Anything that moves through air has to push the air out of its way, and the air pushes back. That push is called air resistance. Another name for it is drag. Air resistance always pushes against the way an object is moving. For a falling cup, that means it pushes up.
A cup by itself is small, so it only has to push a little air aside. The air resistance is weak, and gravity wins easily.
The big sheet at the top of a parachute is called the canopy. When the canopy opens, it catches a huge amount of air. Now the air resistance is strong. It pushes up almost as hard as gravity pulls down.
When the push up matches the pull down, the parachute stops speeding up. It keeps falling, but at one slow, steady speed. A slow landing is a soft landing.
Two cups that are exactly the same. One has a parachute. Which lands first?
A relationship is a connection between two things. When one changes, the other changes too. A parachute is full of relationships. The size of the canopy is connected to the speed of the fall. The weight in the cup is connected to it too. Keep an eye out for what is connected to what.
The canopy and the strings do most of the work on a parachute. Here is what an engineer can change.
The cup is the basket of your parachute. Whatever it carries is called cargo. Pennies, paper clips, and small toys all make good cargo.
More weight means gravity pulls harder. A heavy load falls faster under the same canopy. To give a heavy load a slow fall, you need a bigger canopy.
A cup with no cargo at all can be too light. It may wobble, tip, or even flip over on the way down. A little weight in the cup pulls the strings tight and keeps everything steady.
Put the cargo in the middle of the cup. If the weight sits off to one side, the cup tilts and the parachute drifts.
How you let go matters. Pinch the very center of the canopy and hold it up high, with the cup hanging straight down. Then simply open your fingers. Do not throw it. A throw is not a fair test, and it tangles the strings.
A parachute needs a moment to open. If you drop it from too low, it hits the floor before the canopy fills with air. A higher drop gives the canopy time to do its job.
Engineers measure a parachute by its fall time. That is how many seconds it takes to reach the ground. A longer fall time means a slower, softer landing.
Engineers test their ideas before they build. In this lab you drop a pretend cup parachute from 10 feet up, and a stopwatch times the fall. Change the design, drop it, and see how long it stays in the air.
The fair test rule: change only one thing at a time. If you change two things at once, you cannot tell which one made the difference.
Fall time is the number of seconds from letting go to landing. A longer time means a slower fall.
No two drops are exactly alike, so the same parachute can have a slightly different fall time each time. That is why engineers test more than once.
| Drop | Canopy | Strings | Cargo | Fall time | How it fell |
|---|
No drops yet. Press the green button to drop.
The building steps open when every mission is finished. Here is what you still need to do:
You earned it. Follow each step in order and check the box when a step is done.
Cut the plastic bag open and lay it flat. Use the ruler and marker to draw a square that is 10 inches on every side. Cut the square out. This is your canopy.
Cut four pieces of string that are each 12 inches long. Hold all four together and check that the ends line up. If one is longer, trim it. Even strings make a level parachute.
Bunch one corner of the canopy into a little tail and tie the end of a string around it with a tight knot. Do the same on the other three corners. If the plastic keeps slipping out, press a piece of tape over the string and the corner to hold it.
Punch four holes just under the rim of the cup. Space them evenly, like the 12, 3, 6, and 9 on a clock. If you do not have a hole punch, ask an adult to help you poke the holes with a pencil.
Take the loose end of one string and push it through a hole from the outside to the inside. Tie a knot on the inside, or tape the end down firmly. Do the other three strings the same way. Go around in order so the strings do not cross each other.
Pinch the center of the canopy and lift it up. The cup should hang straight and level. If the cup tilts, one string is too short or too long. Fix that string now.
Put two or three pennies in the middle of the cup. A small strip of tape will keep them from sliding around.
Go to the drop spot your teacher picked. Check that the landing zone is clear. Pinch the center of the canopy and hold it as high as you can, with the cup hanging straight down and the strings untangled.
Your partner holds the stopwatch and says go. Open your fingers and let the parachute fall. Do not throw it. Your partner stops the watch the moment the cup touches the ground.
Write the seconds in your drop log below. Drop the same parachute three times before you change anything, so you can trust your numbers.
Remember the fair test rule. Change only one thing between tests, and write down what you changed. Write the fall time in seconds.
| Drop | What I changed | Seconds |
|---|
| What happened | Why | Try this |
|---|---|---|
| The canopy did not open | The strings were tangled, or the drop was too low | Untangle the strings. Hold it by the center. Drop from higher up. |
| It tilted and slid sideways | The strings are uneven, or the cargo is off to one side | Make the strings match. Move the cargo to the middle. |
| It swung back and forth | Air is spilling out one side, then the other | Cut a vent hole the size of a penny in the center of the canopy. |
| The cup flipped over | The cup is too light | Add a penny. |
| A string came off | The knot or tape let go | Tie a double knot, or add more tape. |
Write three or more sentences. What did you change on your parachute? What happened? Why do you think it happened? Use at least two of these words: gravity, air resistance, canopy, cargo, fall time.
Big idea question: what is the relationship between the size of the canopy and the fall time?
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