This lesson seeks to answer the questions
Why does drag act on a rocket?
Why would a nose cone help a rocket fly higher and straighter?
Activity 1: What is drag?
First, we introduce the concept of air resistance (a.k.a. drag) through a brief conversation. Gather the group together and ask them a series of questions about their experiences in moving vehicles that contact air (in blue). Try to guide their answers toward the ideas covered in the italics
What happens when I stick my hand out into the air from a moving bicycle or car?
The air pushes back against my hand!
What can we say about this force? Where does it push my hand? Does this depend on the vehicle's direction?
The drag force always pushes in the opposite direction of the vehicle's motion.
Does the orientation of my hand matter? What happens if I hold my hand out flat? What if the palm is open?
I feel a stronger push when my hand is open than when it is flat.
The drag force is stronger when there is more exposed surface area facing the direction of motion.
This brief question and answer session brings us to a clear definition of drag.
Drag is the force of air
pushing against a moving object.
Drag always
occurs in opposite direction to motion. More surface area on the leading edge of the object means more drag.
Activity 2: Why a Nosecone?
Why should we add a nose cone? Students should act out this high-energy demo to understand.
- Get students to stand in a clump in the front of the room (they will be “air” particles)
- Have one student volunteer to be the “rocket”
-
Tell the “rocket” to try to move through the “air” with their arms
spread open wide (explain that the reason it is difficult is because
there is too much air resistance)
- Tell the rocket to try to move through the air with their arms pointed in front of them (“rocket with nose cone”)
-
Ask which position made it easier for the “rocket” to move through the
“air,” and what that would mean for the kind of rocket they would need
to make
This exercise helps students grasp that a nose cone helps cut through clumps of air particles and avoid too much contact, which creates a drag force. Hold a quick group discussion to make sure students understand these concepts.
Activity 3: What shape should I choose?
What shape should a nosecone have to help the rocket avoid drag? This demo helps students answer this question through an experiment that compares the drag acting on several different shapes.
The basic idea is that students drop paper models of nosecone shapes over an open air space of at least 10-15 feet height. By observing how long it takes each paper model to fall to the bottom, students understand how much drag is acting on it (longer time = more drag).
DEMOThis video demo gives a first-hand look at how this activity looks. The difference in fall times between models is quite dramatic!
PROCEDUREGather students into groups of five. Within each group, choose one student to be the recorder. This student will be observing which nosecone drops the fastest (and will fill out the activity worksheet (attached below).
Hand out one “nose cone” to each of the remaining group members. Instruct them each drop their nosecones at the same time. Before or after launching, it's a good idea to discuss with the students why releasing at the same time is important.
Place the students in position, hold an exciting count down, then launch/drop the nose cones! Make sure the students are all watching to compare how fast their model fell down. No need to use a stopwatch to measure times exactly, qualitative observation is usually fine.
Once all of the dropping is finished, have students discuss the results they obtained. Make sure they understand why the relative performance of the falling down nosecones might hold true when a rocket is flying upwards.
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 Updating... Ċ Mike Hughes, Jan 23, 2010, 11:24 AM
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