Launch Weights with Rubber Bands

Things Move Launch Weights Purpose with Rubber Bands To compare the distances traveled by launched objects having the same size and shape but different weights. Process Skills Materials Predict, observe, measure, collect data, interpret data, q tape measure communicate, identify and control variables, draw conclusions or meter stick q masking tape Background q permanent marker Objects can be at rest or in motion. To move an object, or to stop an object from moving, a force must be used. It takes less force (per group) to move lighter objects, whereas it takes more force to move q Data Sheet heavier objects. When the same amount of force is applied to q 1 35 mm film canister similar objects that have different weights (masses), the objects or other small will travel different distances. In this activity, students will container with lid use rubber bands that are placed around their feet to launch q 1 extra-long rubber canisters away from their bodies. By standardizing the launch band or several mechanism, students will be able to compare the distances smaller ones traveled by canisters of different weights. q 30 pennies q 1 zippered baggie Time – 45–60 minutes Grouping – Whole class and small groups

Aerial view

Procedure Preparation 1. Collect film canisters ahead of time. Most photo developing labs will save canisters and donate them for a school project if you make a request in advance. Film canisters with lids that fit inside the open end will work best. If canisters are not available, consider similar small containers, such as: plastic baby-food jars with lids, empty yogurt containers with lids, plastic eggs (seasonal), small plastic food-storage containers with lids, or breath-mint tins. 2. Use a permanent marker to draw a line around the midsection of each film canister. This mark will help students be consistent in launching each canister from its center. Figure A

3. Use a 25-foot tape measure to prepare a launch area on the classroom floor, in a hallway, or in another location with a spacious, smooth floor. Attach a 25-foot length of masking tape to the floor in a straight line, and ask student volunteers to help you mark each centimeter and meter (or inch and foot) with small and © iStockphoto.com/Feng Yu

larger dash marks. Using masking tape Donald Erickson © iStockphoto.com/ will eliminate the risk of using a sharp- edged, retractable tape measure with young students. If you prefer that groups not have to take turns launching their canisters, set up more than one launch area. Be sure to leave adequate space between them for 5. Obtain extra-long rubber bands from an safety reasons. office-supply store. When relaxed, these 4. It is important that each launch be made rubber bands are about 18 cm (7 in.) long, from the same starting point and in the and they safely stretch to at least 60 cm same direction so that each group uses (2 ft.). Alternatively, you can link a set of an approximately equal amount of force three normal-sized rubber bands together in each trial. The only significant variable for each group. Provide enough rubber should be the weight of the canister bands for each group. being launched. Use more masking tape 6. Consider assigning roles for each student to mark precisely where each launch within a cooperative group, which may should take place: include group leader, launcher, measurer, • Use masking tape to mark two small canister assembler, and penny counter. squares, one on either side of the zero Keep the number of students in each group mark of the launch line. The near sides small (3–4 students per group). Some of the squares should be 30 cm (12 in.) students may have more than one role. apart. Students who serve as “launchers” Discuss How Objects Move will sit on the ground with their legs Ask students how things move. Discuss a spread slightly in front of themselves variety of objects and encourage students to and will place their heels in these boxes. suggest ways each object can move. Introduce • From the midpoint between the squares, the word force and explain that things move measure 15 cm (6 in.) in the opposite because of a force being used on them. A force direction of the launch. Mark this spot is a push or a pull in any direction. Model a with masking tape in the shape of an X. force in action by slowly pushing and then This will be the launching spot and pulling a nearby object, such as a chair. Invite will standardize how far back students volunteers to carefully demonstrate pushing should pull the rubber band. and pulling other common objects.

Launch Weights with Rubber Bands 5. Model the activity (see Figure A). Place 1. Prepare three film canisters, labeled 0, one long rubber band (or a chain of three 15, and 30, and place the corresponding smaller rubber bands) around both feet number of pennies in each one. Shake of a student volunteer. Coach the student each canister so that students can hear to sit with his or her legs spread and heels that two of the canisters have pennies placed in the masking-tape squares. He inside. Explain that one canister has or she should be facing the long, straight no pennies inside, one has 15 pennies, piece of tape on the ground. Show and one has 30 pennies. Pass the film students a film canister, noting the line canisters around. Ask students which around its midsection. Explain that the one is heavier (the one with 30 pennies) rubber band must be lined up at the line and why (it has the most pennies inside). drawn on the film canister. The launcher should use his or her fingers to hold the 2. Explain the activity. Then invite students top and bottom of the canister, keeping to make predictions about which film it upright, and then release all fingers canister will move the greatest distance at the same time in order to launch it. from its starting point if launched the same way with the same rubber band. Ask Have the student volunteer pull the film students to explain why they made their canister (and the rubber band) toward his prediction. Record students’ predictions or her body until the canister is resting and reasons on the board, and have in contact with the ground on the launch students reflect on them after the activity. pad, which is marked with an X. Ask the volunteer to quickly open his or her 3. Place students into groups and assign fingers when you say “Go!” Once the film roles. Use the data sheet to model canister has been launched, demonstrate recording a prediction. Give a data sheet how to read the measured line of tape to to the recorder in each group. Have each determine the distance that the canister student write the group’s prediction in traveled. Then show students where they the appropriate place. should enter the measurement on their 4. Bring the class to the reserved location data sheet, including the proper units for with a spacious, smooth floor. Make sure measuring length. that students bring their data sheet and TIP: Students may all want to try the pencil. Have the class sit around one of launch themselves. One option is to have the pre-measured and marked launching each student complete his or her own data areas. Explain safety rules, such as: sheet. Alternatively, let all students from • Film canisters may only be launched each group attempt the launch and ask along the ground, not through the air. them to record their own data in a science journal or notebook. Then help students • Film canisters may only be launched by calculate their group’s average distance— pulling the rubber band back to the X. or simply have each group estimate how • Film canisters may only be launched far its canister traveled overall—during if no one is in the launch target area. each trial. If the group shares one data • Film canisters may only be launched sheet, it should record a single when the teacher says “Go.” measurement for each trial.

6. Give each group a film canister, a large 8. Instruct each group to take the tape off the rubber band, and a baggie containing 30 lid and to pour the remaining 15 pennies pennies. Provide masking tape in a central into their zippered baggie, leaving the area. Have students start by putting all 30 canister empty (see Figure D). Students pennies into their film canister and taping should reseal the film canister with the it closed (see Figure B). Once all groups are same amount of tape used earlier. Once ready and film all groups are ready and film canisters canisters are pulled are pulled back to their launch pads, back to their launch call out “Go!” and monitor the launches. pads, call out “Go!” Once again, assist students as needed and monitor the with measuring launches. Remind and recording data. students not to move [Note: The empty the canister until they film canisters may have measured the go farther than the distance and recorded line of tape on the the result on their Figure B ground can measure. data sheet. If so, provide assistance as needed Assist students as needed with measuring so students can the farthest point that the canister reached. measure the total If the launched canister did not travel Figure D distance.] in a straight line and wind up near the measuring tape on the ground, have the 9. Record group results on the board or on launcher try again. (Alternatively, an adult butcher paper. Help students compare helper might help measure the distance in their results with their group’s predictions. any direction by using a tape measure.) 10. Have students record and draw what 7. Instruct each group to take the tape off they learned on their data sheet. the lid and to remove 15 of the pennies, Discussion Questions leaving 15 in the canister (see Figure C). Use these questions to guide a discussion Students should place the removed about the experiment. Encourage students to pennies in a zippered baggie, and they use the words move, heavy, light, force, push, should reseal the film canister with the pull, weight, and distance in their responses. same amount of tape used earlier. Once all groups are ready 1. What made the film canisters move? and film canisters When you stretch out a rubber band and are pulled back to their then release it, it quickly returns to its launch pads, original position. When students let go call out “Go!” and of the canisters, the force of the rubber monitor the launches. band returning to its original position Again, assist students pushed the film canisters forward. as needed with measuring and recording data. Figure C

2. Why did some of the film canisters move Conclusions a greater distance than others? 1. What makes objects move? The film canisters with no pennies inside Force makes objects move. A force can be should move farthest when launched. The film a push or a pull. The rubber bands pushed canisters that had the most pennies should the film canisters forward. move only a small distance by comparison. 2. Why did one of the canisters travel farther When equal amounts of force are used (such than the two others? as the rubber band being drawn back the same distance each time), objects with less weight Empty film canisters do not weigh as much will travel farther. Students might consider as film canisters filled with pennies. It would how far they can throw a small rock versus take more force to make the film canisters filled a big one. with pennies travel as far as the empty film canister traveled. 3. Why did some groups’ film canisters of equal weight travel farther than those 3. What would have happened if the rubber of other groups? bands had been pulled farther? There will almost always be small differences Stretching the rubber band farther (within in the results of experiments. In this activity, safe limits) would have propelled each canister the canister’s shape may have caused it to farther than it traveled during this experiment. tumble differently each time it was launched. More force makes an object move a greater Explain to students that it was important distance. However, there still would have to keep as many things (variables) the same been a difference in distance traveled between during each test so that they were able to focus the empty and full film canisters. on the one thing that was different each time 4. What would have happened if you had they tried the test again. In this case, the only tried launching heavier or lighter objects? thing that should have changed was the weight. Objects that are heavier than the 30-penny 4. What might have happened during this canister would have traveled a shorter experiment if the floor had been bumpier distance. Objects that are lighter than the or rougher (for instance, if it had been empty canister would have traveled a greater covered with carpet instead of tile)? distance. (Things that are too heavy, such as The film canister would not have traveled as a person or a box of books, would not have far in any of the trials if the floor had been moved at all because the force of the rubber bumpy or rough. The texture of the floor would band would not have been great enough. have rubbed against the canister, slowing it Objects that are too light, such as a sheet of down (friction). If the floor had been smoother paper, a feather, or a human hair, would not than the one used, the canister would have have traveled far at all. This is because the traveled farther than it did because there would force of the air resistance that slows their have been little or no texture to slow it down. motion would quickly exceed their momentum, However, unless launched into a very soft due to their shape and/or their small mass.) target that immediately stopped the object regardless of weight (such as water or mud), the film canisters with less weight will likely always travel a greater distance than those with more weight.

Extensions and Variations • Technology: Have students videotape and/or • Variation/Math: Have students help create take pictures of their launches and create a a class graph showing the results of the multimedia presentation about how weight experiment. influences the distance that film canisters • Variation: Allow students to explore what travel. Share the finished products with happens when objects of the same weight another class and with families. but a different size or shape are launched. • Home Connection: Challenge students to Do not let students launch sharp or fragile create their own rubber-band launcher items. at home (with adult supervision) and • Variation: Allow students to explore how bring it to school to explain the results the distance the canister travels is affected of any testing they conducted with it. by the rubber band being drawn back • Research: See Using the Internet in the different distances. Only allow students to Unit Guide for suggested websites to draw the rubber band back a safe distance, extend the learning. and always be sure the launch target area Data Sheet: Students should record their is clear before each launch. predictions and results in the correct places on • Writing: Have students write an acrostic the page. Measurements should be reasonable poem using the word movement, launch, and should include correct units. In the What or force. Each letter should begin a word I learned section, students should explain or phrase related to what students learned that light objects move a longer distance than during the experiment. heavy objects do, when launched with same • ELL/ESL : Create a word wall. Include amount of force. Ideally, students should use content vocabulary such as move, heavy, key vocabulary terms. They should also draw light, force, push, pull, weight (or mass), a diagram and add labels to support their distance, and centimeter (or inch). Also statement. Encourage students to share their include relevant vocabulary from the results and to summarize what they learned. lesson, such as rubber band, film canister, zero, fifteen, thirty, and penny. For more vocabulary resources, visit .

Names______Date______

Prediction: The film canister with (circle one) 30 15 0 pennies will travel the greatest distance because:

30 pennies 15 pennies 0 pennies

Distance: ______Distance: ______Distance: ______

What I learned (write and draw):