Lesson Plan

Force, Motion, & Primitive Technologies

stone arrowhead held in gloved hand

NPS photo

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Grade Level:
Third Grade
Subject:
Physical Science
Duration:
All lessons are 30 minutes
Setting:
outdoors
National/State Standards:
Utah State Science Core Curriculum Topics, Standard Three: Students will understand the relationship between the force applied to an object and the resulting motion of that object.
Keywords:
simple machines, gravity, friction, stone tools, fire making

Overview

Students explore different types of simple machines by examining ancient technologies. Students examine different types of levers using digging sticks and throwing atlatls. They discover how wheels and axles were used to make fire, and how rock wedges can become useful tools.

Objective(s)

PRE-TRIP ACTIVITY
What machine is it?

a. Name two simple machines.
b. Describe two primitive tools.

STATION #1
Atlatls

a. Describe why an atlatl is preferable to a spear.
b. Safely use an atlatl.

STATION #2
Fire

a. Define friction.
b. Explain how to make fire using two pieces of wood.

STATION #3
Digging sticks

a. Explain how a digging stick reduces the amount of force needed to move soil.
b. Use a digging stick to collect food.
c. Name a similar modern day tool.

STATION #4
Stones

a. Describe two jobs for which stone tools were needed.
b. Describe what force is used to make stone tools.

POST TRIP
Draw a Machine

a. Recognize that tools help to overcome force.
b. Name a primitive tool.

Background

Forces are pushes and pulls that can cause an object to change position, motion, or direction. The size and weight of an object can have a direct effect on the amount and type of force needed to cause these changes. Some forces are natural (i.e. gravity and wind). Other forces are manipulated by man (i.e. throwing an object towards another object or driving a car). Friction is created when objects resist an applied force. Often, friction results in heat. The purpose for all machines is to conserve energy. They decrease the amount of force that needs to be applied to create an intended motion.

There are several basic types of simple machines. The incline plane reduces the effort needed to raise an object by increasing the distance it moves. One common form of an incline plane is a wedge, which uses inclined planes to separate things. A lever is a bar that tilts on a pivot. Applying force to one end of the lever produces a useful action at the other end. In a first-class lever, the fulcrum is between the load and the effort. In a second-class lever, the fulcrum is at one end of the bar, the effort at the other, and the load is in the middle. In a thirdclass lever, the fulcrum is at one end of the bar, the effort is in the middle, and the load is at the end. The center of the wheel and axle acts as a rotating lever. The wheel is the outer part of the lever. Friction is a force that appears whenever two surfaces rub against one another. It turns work into heat and sound, instead of useful motion.

Humans have always had to work for a living. During pre-historic times, people used natural materials to create tools that helped them do their work. Wood, stone, bone, and animals provided the raw materials from which they made everything they needed. A considerable portion of modern technology is a result of inventions made hundreds of years ago. The tools that pre-historic people made were both simple and compound machines.

The atlatl is a spear-throwing machine. It is a long stick that you hold in your hand. At one end of the atlatl, there is a notch in which you place the end of a dart. To use the atlatl, you throw with a casting motion (as if you are fishing). A dart thrown with an atlatl has more impact force than a simple bow and arrow and has been known to penetrate car doors and armor. The darts travel at a much higher velocity than if thrown by hand. They can also travel further than a spear thrown by hand. The atlatl is an example of a third class lever. The dart point is an example of a wedge.

Fire is a priority for survival. It is used for warmth, to cook food, to make tools, and much more. It is possible to start a fire using the friction produced by rubbing two sticks together. Rubbing two sticks together creates charred powder. When the powder piles up and gets hot enough, it will ignite. The small pile of dust or coal can be put into tinder and blown into flame. There are many different methods to start fi res by friction. These methods employ simple tools, such as the wheel and axle, levers, and wedges.

One of the primary tools of the hunters and gatherers was the digging stick. It was also an important tool for the agricultural tribes. Archaic people used the digging stick to dig edible tubers out of the ground and to dig for fresh water. Later, digging sticks were used to plant seeds. The wedge-shaped bottom was often fire hardened to add strength to the stick, making it easier to separate the soil. Once the digging stick was in the ground, it acted as a lever to lift the load it needed to get out of the ground.

Stone tools were also important to prehistoric peoples. Stone tools acted as both levers and wedges. Scraping motions were like a second-class lever. When sawing and cutting, Ancient Puebloans used stone tools as a wedge. Although we often think of multi-strike creations, such as arrowheads and spear points, when we think of stone tools, more often than not, tools were simple one-strike scrapers and knives. Simple stone tools can be made with river rocks. By hitting the corner of a lens shaped rock on a harder rock, you can make a simple or discoidal blade.

Procedure

Extensions

PRE-TRIP ACTIVITY
What machine is it?

Have students pick four objects from their classroom. Have students describe what type of machine each object is and draw the object labeling the machine’s parts.

STATION #3
Digging sticks

Have students use field guides to find other plants with useful roots. Discuss how each plant was collected, stored and used.

STATION #4
Stones

Have each student pick one artifact out of the points you brought. Have each student write a story about how the point was made, used and discarded.

Additional Resources

London, J. (1993). Fire race. San Francisco, CA: Chronicle Books.

Macaulay, D. (1988). The way things work. Boston, MA: Houghton Mifflin.

O’Brien, K. & White, R. Petroglyph National Monument teachers guide. Albuquerque, NM: Petroglyph National Monument.

Vocabulary

distance, force, gravity, weight, motion, speed, direction, simple machine, temperature, degrees, lubricated, heat source, friction.