26 the Wheel and Axle © Delta Education

ivi act ty 26 TheThe WheelWheel andand AxleAxle

BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN Grade 3—Quarter 3 Activity 26

SC.C.1.2.1 The student understands that the motion of an object can be described and measured.

SC.H.1.2.1 The student knows that it is important to keep accurate records and descriptions to provide information and clues on causes of discrepancies in repeated experiments.

SC.H.1.2.2 The student knows that a successful method to explore the natural world is to observe and record, and then analyze and communicate the results.

SC.H.1.2.3 The student knows that to work collaboratively, all team members should be free to reach, explain, and justify their own individual conclusions.

SC.H.1.2.4 The student knows that to compare and contrast observations and results is an essential skill in science.

SC.H.1.2.5 The student knows that a model of something is different from the real thing but can be used to learn something about the real thing.

SC.H.3.2.2 The student knows that data are collected and interpreted in order to explain an event or concept.

ACTIVITY ASSESSMENT OPPORTUNITIES The following suggestions are intended to help identify major concepts covered in the activity that may need extra reinforcement. The goal is to provide opportunities to assess student progress without creating the need for a separate, formal assessment session (or activity) for each of the 40 hands-on activities at this grade level.

1. Remind students that they used rollers in the previous activity. Ask, How are rollers different from a wheel and axle? (Rollers act like a lubricant and reduce the amount of force it takes to move an object. A wheel and axle multiplies a force to make work easier.)

broward county hands-on science Quarter 3 269 © Delta Education. Photocopying and distribution prohibited. 2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the activity.

In addition to the above assessment suggestions, the questions in bold and tasks that students perform throughout the activity provide opportunities to identify areas that may require additional review before proceeding further with the activity.

270 activity 26 The Wheel and Axle © Delta Education. Photocopying and distribution prohibited. ivi act ty 26 TheThe WheelWheel andand AxleAxle

OBJECTIVES PREPARATION Students are introduced to a second type of 1 Make a copy of Activity Sheet 26, Parts A simple machine: the wheel and axle. and B, for each student. The students 2 Cut a 1-m (3-ft) length of string for each team of two. identify the parts of a wheel and axle observe how force gets transferred 3 Each team will need a wooden dowel, two between the wheel and the axle wooden wheels, a length of string, a stack of washers (taped together), and a piece use a wheel and axle to lift a load of masking tape. investigate the tradeoff of force for distance when using a wheel and axle 4 This activity begins with a demonstration of machine a doorknob—a type of wheel and axle machine. Check to see if your classroom door has a doorknob. If it doesn’t, try to find SCHEDULE a door nearby that does for students to visit About 40 minutes briefly. As an alternative, bring a doorknob mechanism to class for students to VOCABULARY examine. axle wheel and axle BACKGROUND INFORMATION A rotating wheel helps us do work by reducing MATERIALS friction between an object and the surface over which it moves. Attaching an axle to a wheel For each student turns the device into a simple machine, one 1 Activity Sheet 26, Parts A and B that can be used to transmit and magnify force. 1 pr safety goggles* In a wheel and axle machine, the wheel and the axle are attached, such that turning the For each team of two wheel causes the axle to turn also (and vice 1dowel versa). Because they turn together as a unit, any force that is applied to the wheel gets 1 set washers, stacked and taped transferred to the axle. (from Activity 24) 2 wheels, wooden However, because the wheel and axle are of different sizes, force gets modified as it is For the class transmitted: A small force applied over a long 1 pair scissors* distance (the circumference of the wheel) is converted into a larger force applied over a 1 roll string shorter distance (the circumference of the 1 roll tape, masking axle). The greater the difference in size Delta Science Reader Force and between the wheel and axle, the greater the Motion magnification of force as it is transmitted from wheel to axle (see Figure 26-1). *provided by the teacher broward county hands-on science Quarter 3 271 © Delta Education. Photocopying and distribution prohibited. Activity Sheet 26, Part A A doorknob is a good example of a wheel The Wheel and Axle and axle machine (see Figure 26-2). A doorknob receives a manually applied force 1. All of these objects are wheel and axle machines. Label the wheel and the axle in each picture. at the knob (the wheel) and magnifies the force at the shaft (the axle) to accomplish the work (releasing the latch so the door wheel can be opened). Try removing the knob and wheel turning the shaft with your fingers. It’s axle nearly impossible to open a door that way. axle

small force applied over a long distance Screwdriver Faucet

large force wheel axle applied over a short distance axle wheel

Steering Column Rolling Pin

Figure 26-1. Like all simple machines, a wheel and axle

transmits and magnifies force. Activity Sheet 26, Part B In this activity, students use a wheel and y axle machine to lift a load. By adding and The Wheel and Axle

removing wheels from an axle, students 2. What happened to the axle when you turned the wheel? learn how a wheel and axle machine can The axle turned too.

help make work easier. 3. What happened to the wheel when you turned the axle? The wheel turned too.

4. Are the wheel and the axle the same size? no large force applied over Which is bigger? the wheel a short distance 5. Do you think it will take more effort or less effort to lift the washers by turning the wheels? less effort

6. Did it take more effort or less effort to lift the washers by turning the wheels? less effort using the wheels

7. How many turns did it take to raise the washers:

by turning the dowel? Answers will vary. small force applied over a long distance by turning the wheels? Answers will vary; 2 to 3 times as many turns as when using the dowels

8. What is the tradeoff when using a wheel and axle to do work? Figure 26-2. A doorknob works like a wheel and axle. You can use less force by turning the wheel, but the force must be applied over a greater distance.

272 activity 26 The Wheel and Axle © Delta Education. Photocopying and distribution prohibited. Guiding the Activity Additional Information 1 Invite a student volunteer to open the classroom door. Ask the student, What did turn the doorknob you have to do before you could pull the door open?

Invite several other students to examine and describe the doorknob. Ask, What does it The doorknob is round. It is attached to a look like? How is it attached to the door? “neck” (a narrow shaft) that is inserted directly into the door. Tell students that a doorknob is really a wheel and axle, which is a second type of simple machine. Write the term wheel and axle on the board.

Draw a simple doorknob on the board. Show the round knob attached to a narrow shaft. Underline the word wheel on the board. Ask, Which part of the doorknob do you Students will probably guess correctly that think is the wheel? the knob acts as the wheel.

Underline the word axle on the board. Tell students that an axle is a shaft that is inserted into the middle of a wheel. Ask students, Which part of the doorknob is The axle is the narrow shaft, or “neck,” to the axle? which the knob is attached.

Tell students that wheel and axle machines are all around us. Distribute a copy of Activity Sheet 26, Parts A and B, to each student. Tell students to label the wheel and the axle in each picture in question 1. When students have finished, tell them they are going to learn how wheel and axle machines help make work easier. 2 Divide the class into teams of two, and distribute one wooden wheel and a wooden wooden wheel dowel to each team. Have students insert the dowel into the hole in the center of the wheel to make a wheel and axle machine (see Figure 26-3). If the wheel and dowel are a wooden dowel (axle) little loose, have students put a small piece of masking tape around the dowel before inserting it into the wheel for a tighter fit. Figure 26-3. A wheel and axle.

broward county hands-on science Quarter 3 273 © Delta Education. Photocopying and distribution prohibited. Guiding the Activity Additional Information Tell students to turn the wheel and note what When the wheel is turned, the axle also turns. happens to the axle. Instruct them to answer question 2 on their activity sheets.

Now have students turn the axle and note When the axle is turned, the wheel also turns. what happens to the wheel. Instruct them to answer question 3 on the sheet.

Explain that because the wheel and axle are attached, when force is applied to one end, it gets transferred to the other end. In other words, when a turning force is applied to the wheel, that force or effort gets transferred to the axle, causing it to turn too. Likewise, when force is applied to the axle, the force or effort gets transferred to the wheel.

Ask, What do you think would happen to The force would not get transferred. The the force if the wheel spun freely around wheel must be attached to the axle in order the axle? for force to be transferred. 3 Now ask students to note the difference in size between the wheel and the axle. Ask, Which is bigger? Instruct students to The wheel is bigger. answer question 4 on the activity sheet.

Ask, What effect do you think this Accept all reasonable answers. difference in size has on how the wheel and axle works? Tell students to remove the wheel from the dowel. Distribute a second wooden wheel, a length of string, a stack of washers (taped together), and a small piece of masking tape to each team. Have students tie one end of the string To tie the string around the washers, have through the washer holes and around the students thread the end through the hole in stack of washers. Have them tie the other the stack. end to the middle of the dowel and secure it with tape. Note: Students may need help threading the string through the hole in the washer stack and tying a secure knot.

274 activity 26 The Wheel and Axle © Delta Education. Photocopying and distribution prohibited. Guiding the Activity Additional Information Tell students to lift the stack of washers with the dowel. Then instruct them to turn the dowel with their fingers to wrap the string around the dowel and raise the washers (see Figure 26-4). Students should keep their hands at a steady height. Have the students in each team take turns and note how much effort this takes.

Figure 26-4. Raising the washers by turning the dowel (axle). 4 Next, tell students to unwind the string from around the dowel. Have them attach a wheel to each end of the dowel. Ask, Do you think Accept all reasonable answers. it will take more effort or less effort to lift the washers by turning the wheels? Instruct students to answer question 5 on the activity sheet.

Tell students to lift the washers off their desk and turn the wheels to wind the string and raise the washers. Again, they should keep their hands at a steady height (see Figure 26-5). Tell them to take turns and note how much effort it takes.

Figure 26-5. Raising the washers by turning the wheels.

When all students have had an opportunity to raise the washers, ask, Did it take more effort or less effort to raise the washers by It seemed to take less effort using the wheels. turning the wheels? Tell students to answer question 6 on the activity sheet.

Ask, Did the weight of the stack of washers no change?

broward county hands-on science Quarter 3 275 © Delta Education. Photocopying and distribution prohibited. Guiding the Activity Additional Information 5 Have students unwind the string from around Let students make a mark on the dowel with the dowels and remove the wheels. Tell them a pencil so they can keep track of rotations. to turn the dowel with their fingers and count how many turns it takes to raise the washers. Assuming a string length of about 60 cm Tell students to count the number of times (24 in.) after tying the knots, it should take they must twist their wrists (like turning a students approximately 30 turns to raise the doorknob). Tell them to record the number in washers up to the dowel. You may want to try question 7 on the activity sheet. it yourself to see. Now have students unwind the string, It should take students anywhere from 80 to reattach the wheels to the ends of the dowel, 90 turns to raise the washers up to the and turn the wheels again to raise the dowels. washers. Tell them to count the number of turns it takes to raise the washers this time and record the number on their activity sheet.

When all teams have finished, ask, Did it take by turning the wheels more turns to raise the washers by turning the dowel or by turning the wheels?

Ask, Why did it take so many more turns Guide students to understand that because when turning the wheels? the wheel is so much bigger than the dowel axle, it must be moved a greater distance in order to make the axle move a small distance. Explain the tradeoff of force for distance with If students have trouble understanding this, the wheel and axle: It takes less force to lift try drawing Figure 26-1 on the board for the washers by turning the wheel, but the them. force must be applied over a greater distance. In other words, a small force applied over a long distance—the distance around the wheel—is converted into a larger force applied over a shorter distance—the distance around the axle. 6 Finally, remind students of the doorknob. Ask, How do doorknobs make opening You use less force turning a knob than you doors easier? would turning the shaft, but the force must be applied over a longer distance. Instruct students to complete question 8 on their activity sheets, and review their answers as a class. Then tell them that in the next activity, they are going to learn about a special type of wheel with teeth, called a gear. 7 As appropriate, read or review page 7 of the Delta Science Reader Force and Motion.

276 activity 26 The Wheel and Axle © Delta Education. Photocopying and distribution prohibited. REINFORCEMENT SCIENCE AT HOME Ask students how they could use even less Students are likely to be aware of wheels force to raise the stack of washers. (Answer: outside, on cars, trucks, wagons, bicycles, They could increase the size of the wheels.) and so on. Ask them now to be on the Ask students to predict what increasing the lookout for wheels inside the house. See size of the wheels does to the number of turns who can find wheel and axle machines in they must make to raise the washers. (Answer: unusual places at home. Let them make up The larger the wheels, the more turns students riddles about the wheels and the work they must make to raise the washers.) do, and try to stump the class. (“Turn me and you will soon be able to run through the sprinkler. What wheel am I?” The SCIENCE JOURNALS outside faucet.) Have students place their completed activity sheets in their science journals.

CLEANUP Have students remove the wheels and the strings from the dowels. Tell them to leave the string tied around the washers. Collect the wheels, dowels, and washer sets, and return them to the kit.

Science Challenge students can research the use of windmills, the paddle wheel, and the water wheel Tell students that a wheel can be thought of throughout history. Ask them to find out how as a series of levers rotating, or moving, the rotation of a windmill or a water wheel is around a fulcrum that is in the center. To used to drive other wheels and parts to demonstrate this, have students carry out perform a task such as grinding grain or this activity. Attach four drinking straws to the sawing lumber. Encourage groups to present center of a foam plastic plate, spaced evenly their findings in oral reports accompanied by around the plate. Push a dowel or a nail drawings or pictures cut from magazines. through the center of the plate and the straws. Tape the ends of the straws to the plate. Then, holding the dowel protruding Science and the Arts from the back of the plate, put a finger against the end of one straw and turn the Have students add examples of wheel-and- plate slowly. Students should see that the axle machines to the bulletin board display straws function as levers that continuously of simple machines they began in Activity “tip” in one direction. If students have 23. Continue encouraging them to be difficulty perceiving this, have them use creative in their additions to the display, straws of different colors or color the straws using actual objects and three-dimensional with felt-tip markers. models as well as pictures.

If you have students carry out the Science, Science, Technology, and Society Technology, and Society or Science and Windmills, which have been used for Social Studies connections, you might as centuries to grind flour and pump water, are an extension let students construct a being used today to run machines and to simple windmill in the form of a pinwheel. generate electricity. The wind turbine, the Each student will need a piece of modern counterpart of the windmill, drives a construction paper or colored plastic, a 1 generator rather than a grindstone. To extract wire nail, and a ⁄4-in. (6-mm) dowel, 2 to as much energy from the wind as possible, 3 ft (60 to 90 cm) long. Have students cut the rotor blades are huge, up to 100 meters the construction paper or plastic into an 1 (330 feet) across. Stimulate students’ interest 8 ⁄2-in. (20-cm) square. (Before proceeding in these devices by showing them a further, students may want to decorate the photograph of a large wind farm, such as the material with crayons, felt-tip markers, or one at Altamont Pass near San Francisco, glitter glue.) Then cut each of the corners California. Suggest that interested students of the square toward the center to within 1 3 find out about the use of wind as an ⁄2 to ⁄4 in. (1 to 2 cm) of the center. Curl alternative to burning fossil fuels to produce each corner to the center without folding energy. How well do wind turbines work? the material. Use the nail and a small What are their advantages? Their hammer to tack the corners at the center disadvantages? to the dowel, just below one end of the dowel. Tack loosely enough to permit the windmill to spin. Hold the windmill in the Science and Social Studies wind (or blow on it) and watch it spin. Encourage students to speculate how they Three other examples of the wheel and axle could make their windmills do work. are the windmill, the paddle wheel, and the water wheel. Working in small groups,