6 Figure 1: Three weights suspended from a bar Above is a drawing of three strings hanging from a bar. The three strings are made from identical materials and have weights attached to their ends. String 1 and String 3 are the same length. String 2 is shorter. A 10 unit weight is attached to the end of String 1. A 10 unit weight is also attached to the end of String 2. A 5 unit weight is attached to the end ofthe String 3. The strings (and attached weights) can be swung back and forth, and the time it takes to make a swing can be l-imnrl Figure 1: Three weights suspended from a bar Above is a drawing of three strings hanging from a bar. The three strings are made from identical materials and have weights attached to their ends. String 1 and String 3 are the same length. String 2 is shorter. A 10 unit weight is attached to the end of String 1. A 10 unit weight is also attached to the end of String 2. A5 unit weight is attached to the end of the String 3. The strings (and attached weights) can be swung back and forth, and the time it takes to make a swing can be timed. Use figure 1 and the description above to answer the next two questions. Which of the following statements would be an appropriate hypothesis for a swing experiment that only uses strings 1 and 2? {I} The time it takes to swing back and forth is different on the moon than on Earth. 0 The time it takes to swing back and forth is different for different string materials. {I} The length of the string affects the time it takes to swing back and forth. {I} The weight on the string affects the time it takes to swing back and forth. QUESTION 2 (Refer to figure 1 and the description in question 1) Fora swing experiment that uses only strings l and 2. what are possible independent and dependent variables? 'fhe independent variable would be the force of gravity, and the dependent variable would be the time for the back and forth swing. 'fhe independent variable would be the density of the string. and the dependent variable would be the time for the back and forth swing. O The independent variable would be the length of the string. and the dependent variable would be the time for the back and forth swing. 'fhe independent variable would be the weight on the string. and the dependent variable would be the time for the back and forth swing. \fRED LIGHT Figure 2: Four sealed glass tubes lled with fruit flies and exposed to red light As shown in the figure above, twenty fruit flies are placed in each of four glass tubes. The tubes are sealed. Tubes | and II are partially covered with black paper; Tubes Ill and IV are not covered. The tubes are placed as shown. Then they are exposed to red light for ve minutes. The number of flies in the uncovered part of each tube is shown in the drawing. Use figure 2 and the description above to answer the next two questions. This experiment shows that ies respond to (respond means move to or away from): O red light but not gravity -::IIIZ:- gravity but not red light -.:III:.- both red light and gravity -::IIIZ:- neither red light nor gravity QUESTION 4 (Refer to figure 2 and the description in question 3) A reasonable explanation for your answer to question 3 is because ... O most flies are in the upper end of Tube Ill but spread about evenly in Tube II. O most flies did not go to the bottom of Tubes I and III. O the flies need light to see and must fly against gravity. O the majority of flies are in the upper ends and in the lighted ends of the tubes. O some flies are in both ends of each tube.QUESTION 5 The gure below at the left shows a drinking glass and a burning birthday candle stuck in a small piece of clay standing in a pan of water. When the glass is turned upside down, put over the candle, and placed in the water, the candle quickly goes out and water rushes up into the glass (as shown at the right). Figure 3: Before and after a glass Is placed over a burning candle In a pan of water. This observation raises an interesting question: Why does the water rush up into the glass? Here is a possible explanation. The flame converts oxygen into carbon dioxide. Because oxygen does not dissolve rapidly into water but carbon dioxide does, the newly formed carbon dioxide dissolves rapidly into the water, lowering the air pressure inside the glass. Suppose you have the materials mentioned above plus some matches and some dry ice (dry ice is frozen carbon Suppose you have the materials mentioned above plus some matches and some dry ice (dry ice is frozen carbon dioxide). Using some or all ofthe materials. how could you test this possible explanation? {I} Saturate the water with carbon dioxide and redo the experiment noting the amount of water rise. The water rises because oxygen is consumed, so redo the experiment in exactly the same way to show water rise due to oxygen loss. {3- Conduct a controlled experiment varying only the number of candles to see if that makes a difference. (-1 suction is responsible for the water rise, so put a balloon over the top of an open-ended cylinder and place the cylinder over the burning candle. |'_\\| Redo the experiment. but make sure it is controlled by holding all independent variables constant; then measure the amount of water rise. QUESTION 6 (Refer to figure 3 and the description in question 5) What result of your test (mentioned in question 5 above) would show that your explanation is probably wrong? {I} The water rises the same as it did before. 0 The water rises less than it did before. {I} The balloon expands out. {I} The balloon is sucked in