Bring Science Home An aerodynamic activity from Science Buddies Key concepts Aerodynamics Drag Flight Forces Introduction Background As the skydiver is falling, the force of gravity is pulling the person and his or her parachute toward the earth. The force of gravity can make an object fall very fast! The parachute slows the skydiver down because it causes air resistance, or drag force. The air pushes the parachute back up and creates a force opposite to the force of gravity. As the skydiver falls, these "push and pull" forces are nearly in balance.* Materials Preparation • Securely tape two pennies to the end of the strings on each square. What do you think the purpose of the pennies is? Hint: you can try letting the squares float to the ground without the pennies first and see what happens. Procedure • Release the smaller parachute from high above the ground and time how long it takes for it to fall to the ground. Try this parachute two more times, releasing it from the same height each time. About how long did it take to fall on average? Observations and results How large a parachute is (in other words, the parachute's surface area) affects its air resistance, or drag force. The larger the parachute, the greater the drag force. In the case of these parachutes, the drag force is opposite to the force of gravity, so the drag force slows the parachutes down as they fall. Consequently, the larger parachute, with its greater drag force, takes longer to reach the ground than the smaller parachute. Although the force of gravity is greater on the larger, slightly heavier parachute than the smaller, lighter one, the relative increase in the drag force on the larger parachute is greater than the increase in the force of gravity. *Correction (9/19/12): The last sentence in this paragraph, which erroneously described the effect of drag and gravity on the skydiver, was removed after posting. More to explore Calculating Drag from Aerocon Skydiving from the Physics Classroom Parachute Descent Calculations from Randy Culp Parachutes: Does Size Matter? from Science Buddies This activity brought to you in partnership with Science Buddies Discover world-changing science. Explore our digital archive back to 1845, including articles by more than 150 Nobel Prize winners. Subscribe Now!
Tools and Materials
Assembly
To Do and NoticeTake 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? What’s Going On?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. Going FurtherCan 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? Teaching TipsEncourage 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.
Listen to the rhythm of falling weights.
“g,” that’s interesting! Investigating gravity.
Suspend a ball in a stream of air. |