What You Need:
- 3 small plastic bags (not zip-lock kind) or 12 inch pieces of plastic cut from a trash bag or grocery bag.
- Some string
- 3 small stones of different sizes.
- Masking tape
To Do and Observe:
Make 3 small parachutes; each one weighted with a different size stone. 1. Cut 12 lengths of string, each 20 inches long. 2. Use a paper clip to punch four holes, equally spaced around the opening of each bag. 3. Tie a separate string into each small hole, and let the strings dangle down below the bags. 4. Use a piece of masking tape to secure the string ends to a stone. 5. Do this with each bag. Test your parachutes! 6. Next, arrange your parachutes in order; small, medium and largest stone. Take them outside. 7. Loosely wrap the string and baggy around each stone. 8. Throw each parachute up into the air and observe the time it takes for each one to reach the ground. 9. Time several tries for each parachute if you wish to get an idea about which parachute falls to the ground fastest and slowest.
What's Going On:
Gravity is the universal force of attraction in space. It pulls objects with mass together, keeps planets in orbital motion, and holds you and me firmly grounded on Earth.
Gravity pulls down equally on all your falling parachutes. But each one must push against the resisting force of air molecules in the atmosphere as it travels earthward. Depending upon its size, each of your stones has a different surface area and weight! Those stones with larger surface areas and lighter weights fall at a different rate than heavier stones with smaller surface areas. Stones of equal weight, yet different surface areas will fall to earth at different rates.
Now, imagine doing the same experiment using both large and small plastic bags.
Try to make sure that the stones are securely fastened to the parachutes with masking tape. Also, the tape itself has weight and will create a resistance to falling. So equal amounts of tape are encouraged for each parachute.