Kinematics-Alliston
From wiki.NGSciEd.org
Whirligig Challenge
Created By: Lisa Alliston
GPS: S8P3 Students will investigate the relationship between force, mass and the motion of objects.
Elements: a. Determine the relationship between velocity and acceleration. b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia and friction.
GPS: S8P5 Students will recognize characteristics of gravity, electricity and magnetism as major kinds of forces acting in nature.
Elements: a. Recognize that every object exerts gravitational force on every other object and that the force exerted depends on how much mass the objects have and how far apart they are.
Grade Level: 8th
Background Knowledge
Forces in Aggregate - when an object drops to the ground, it will have two forces acting upon it: gravity pulling the object down and air resistance pushing the object up. The resulting force is called the net force. When an object falls, the net force of gravity is greater than the force of air resistance (or else the object would remain in the air). Objects change motion not from force but from net force.
Newton’s First Law of Motion states an object in motion will stay in motion or an object at rest will stay at rest unless acted on by an unbalanced force. Every change in motion is considered an acceleration speeding up slowing down
Balanced forces = no change in motion Unbalanced forces = change in motion
Changes in motion signal the existence of a net force.
Velocity is a measure of a change in position over time. We note an object’s change typically as speed. Velocity is usually expressed not only with speed but a vector heading or direction.
Since acceleration is a change in motion, then changes in velocity must signal acceleration . . . and thus net force. Different objects can experience the same force, but the response to that force is different. The mass of the object determines the effect of the net force.
Background Knowledge Activity
Using several items students are familiar with, we will drop objects simultaneously and predict/observe/explain which ones land first. This will allow students to experience and explain surface area as well as air resistance.
1.Drop a book and piece of paper at same time.
2.Drop 7 stacked coffee filters and one coffee filter.
3.Drop 7 coffee filters that are taped together (long ways) and one coffee filter.
4.Drop a book and a crumbled piece of paper.
5.Drop a flat paper on top of a book.
See following chart to fill in with predictions, observations and explanations.
Integration of Science Concepts
Students will investigate the relationship between mass and the motion of objects as they modify their whirligig by adding/taking off paper clips and changing the surface area of the wings.
Students will also determine the effects of balanced and unbalanced forces as they observe the whirligig hesitate in the air before gravity takes over. Inertia will also be observed as well as friction (air resistance).
Students will investigate the rate of a whirligig's acceleration and the properties that determine it.
Common Misconceptions
An object at rest has no energy.
If an object is at rest, no forces are acting on the object.
Smaller objects (surface area) fall slower than larger ones. Smaller area = less mass and will fall slower.
Inquiry Science Lab Activity
Cereal companies like to attract attention to their products. One company prints a paper helicopter on the back of its cereal box for children to play with. They call their simple paper helicopter a whirligig. The whirligig is cut out from the box. Parts of it are folded and paper clips are attached. When a child drops the whirligig, it spins as it falls.
The cereal company wants to create a new whirligig that will fall more slowly than the one they have been using. They think that would be more fun.
Your challenge is to determine how to make a whirligig that will fall more slowly than the current one. The company gives you the criteria and constraints.
Purpose of Lab
The purpose of this lab is to determine the affects gravity, inertia and friction have on an object.
Questions
1. How can I make a whirligig fall more slowly than the one on the box?
2. What affects the rate at which an object falls?
3. What is the structure of the item I’m working with?
4. What are its mechanisms?
5. How is this items supposed to behave? What might I change in the item to affect that behavior?
Safety Rules
All standard safety rules apply. Students should be aware of how to properly use scissors.
Hypothesis
Read the introduction as to what the cereal company is asking of you. Write a hypothesis of how you think you will be able to slow down the whirligig.
Materials
Whirligig templates Scissors Paper clips Stopwatch
Procedure
1. Craft a whirligig from the basic template you have been provided.
2. Complete several trials to time and observe how it falls to the ground.
3. Record your data and answer questions on your handout.
4. Discuss as a group what changes you could make to your whirligig to make it fall more slowly.
5. Complete your planning sheet.
6. Design and test those changes with by timing and observing several (more than 5) trials.
7. Record your observations.
Conclusion
Was your hypothesis correct? Explain why or why not.
How Misconceptions Will Be Addressed
An object at rest has no energy: Students will observe the whirligig's hesitation before falling and conclude the energy required to cause it to fall was still present at rest.
If an object is at rest, no forces are acting on the object: Students will observe the hesitation before the whirligig falls and will conclude gravity and air resistance were still acting on it when it was momentarily at rest.
Smaller objects will fall slower than larger ones. By increasing the surface area and making the object larger, it will increase air resistance and take longer to fall.
Resources
Gallagher &, S. (2008, June). Diving into Science. Paper presented at Physics Inquiry for
- Student Achievement funded by Forsyth and Gwinnett Counties, Forsyth County Board of Education.
5 Topic-Related Internet Resources
Middle School Science. (2000). Retrieved August 31, 2009, from
- Http://www.middleschoolscience.com/physics.html
Physical Science. (2006). The NSTA Learning Center. Retrieved August 31, 2009, from
The Science Spot. (n.d.). Retrieved August 31, 2009, from
Glasser, H. (2000, March). Serendip. Retrieved August 31, 2009, from
Discovery Education. (2008). Retrieved August 31, 2009, from
