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Grade Level (s): 7- 8
Introduction: Our common experience is that objects in motion do not often stay in motion. In real life when we move or try to move one object against another, there are interactions or forces that resist that motion. Friction force is the force that opposes the motion or the tendency of motion between surfaces in contact. The mechanism that retards the motion is called friction.
When friction opposes a motion in progress it is called dynamic or kinetic friction. When friction prevents a motion from occurring, it is called static friction. Friction is present in all states of matter whether solid, liquid or gaseous. The study of forces and motions in fluids is called fluid mechanics. When examining vessel hull design, not only is the shape of the hull important, so is the surface texture of the hull. Friction between solids and liquids depends upon more factors than just the shape of the solid immersed in that fluid. Dynamic friction between solids depends on the normal force on the object and the materials of the surfaces in contact as well as the texture of the surfaces. This lesson plan will examine how friction affects vessel hull design.
Learner Objectives:
- The student will be able to understand the concept that friction between solids and liquids depends upon both the shape and surface texture of the solids (the hull) moving through fluids (i.e. the ocean).
- The student will be able to understand that friction depends upon the materials in which contact occurs.
- The student will be able to understand that friction usually takes away energy in motion changing it into heat.
Florida Sunshine State Standards: Science: SC.C.1.3.1, SC.C.2.3.3, SC.C.2.3.3, Math: MA.E.1.3.1, MA.D.1.3.2
Competency-Based Curriculum: Science:.M/J-I-8-A, Math: M/J-I-V-2-A, M/J-3-IV-6-A
Materials:
Paper
White glue
Water
Large plastic containers
Pencils
Varnish
Sand
Rubber band
Paintbrush
Paint thinner
Sandpaper
Activity Procedures:
- Have a small group of selected students stand and run in place. Brainstorm as to why students were able to walk and run introducing the concept of friction.
- Have the students rub one hand against the other introducing friction as a force that changes energy in motion to heat.
- Define and explain the following terms: solid, liquid, gas, hull, friction, dynamic or kinetic friction, static friction, and fluid dynamics.
- Access prior knowledge by introducing and discussing how cars and bicycles are aerodynamically designed. Begin discussion on how boats’ hulls are shaped. Contrast white water kayaks (flat, smooth hulls to maximize slide and minimize direction) and canoes (straight, deep “v” hulls to minimize slide and maximize direction). Discuss various hull shapes.
- Place students in cooperative learning groups and have each group design, build and draw their own hull designs using paper mace.
- Introduce the concept of fluid dynamics and water repellent polymer coatings (FCAT supplemental with corresponding content have been included at the conclusion of this lesson plan.)
- Using one regular pencil and one altered pencil (coated with varnish mixed with coarse sand particles), teacher will demonstrate the pencil coated with sand will encounter more friction and its velocity will decrease. A modified sling shot and long plastic container filled with water will be used to “race” the two pencils.
Students can then be given similar containers (without the launching device) and pencils to verify that the smooth surface pencils encounter less friction.
Student Assessment:
Teacher will monitor student participation in brainstorming activity (1), boat hull paper mace (4) construction and pencil-hull friction lab (6).
Teacher will prepare critical thinking skills questions for the students during the lab and discussion activities.
Activity Extensions:
- Have students calculate the coefficient of dynamic friction for textbook moving on two desks: one smooth wooden desk and another where sandpaper covers the desk. The formula for dynamic friction is as follows: F stands for friction, m stands for coefficient of friction and N stands for the normal force: F = mN
Wooden Desk:
F= 6 Newtons N=20 Newtons Answer: m=0.3
Wooden Desk coated with sandpaper
F= 18 Newtons N= 20 Newtons Answer: m=0.9 (Math)
- Have the students write an essay about Christopher Columbus’ voyage to the new world. (Language Arts and History)
Friction Exercise Sheet:
1. What is friction?
Answer: Friction is a force that always opposes the motion between two surfaces in contact.
2. Is friction only present in solids?
Answer: No, friction is present in any state of matter.
3. How can we reduce friction between solids and liquids?
Answers may vary.
By changing the shape of the solid, by putting some repellent material on the solid object.
Home Learning Activity:
Have the students research hull designs on the Internet and/or provide handouts on hull design prior to activity number four.
Vocabulary: solid, liquid, gas, hull friction, dynamic friction, kinetic friction, static friction, fluid dynamics
References/Related Links:
http://jin.jcic.or.jp/trends98/honbun/ntj970609.html
http://www.ise.bc.ca/WADEhullform.html
American Red Cross (1997). Start sailing right. Portsmith, RI: United States Sailing Association
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