Clicker Questions for NEXUS/Physics Fluids A note on usage: The clicker slides in this booklet are meant to be used as stimuli to encourage class discussion. They are intended for use in a class that attempts to help students develop a coherent and sophisticated understanding of scientific thinking. They are NOT intended as items to test whether students are “right or wrong” or “know” the correct answer by one-step recall if enough cues are given. This has a number of instructional implications that are reviewed in general on the next four slides. The individual slides also contain annotations discussing their intended use. Usage: 1 • Feedback One of the most important values of a clickerresponse system is to provide instructors with some understanding of what students are thinking. Good clicker questions can be highly revealing (and surprising). But the critical fact is not that the students make mistakes but to use those mistakes to probe their thinking and find out why. This raises the importance of a rich subsequent discussion well above “letting the students know what the right answer is.” Usage 2: • Student-student interactions The critical value for student learning occurs in what happens after a clicker question has obtained a mixed response from the students. The standard next cue is, “Find someone who disagreed with the answer you chose and see if you can convince them.” After a minute or two of discussion, a second click may show students having moved dramatically towards the correct answer. A brief call for who changed their answer and why can lead to a useful exchange. When they have not moved significantly, more discussion is called for. Usage: 3 • Incompletely specified questions Some items have questions that are simple if idealized assumptions are made, subtler if they are not. Part of the discussion of these items are intended to include issues of modeling, idealizations, and hidden assumptions. • Questions where answers are not provided. In these items, the intent is to have students come up with potential answers and have the instructor collect them and write them on the board. Occasionally, especially at the beginning of a class, it may take some time before students are willing to contribute answers. It can help if you have some prepared answers ready, walk around the class, and put up the answers as if they came from the students. This can help students get more comfortable with contributing. Usage: 4 • Cluster questions Some questions are meant to be used as part of a group of questions. In this case, resolving the answers to individual questions is better left until the entire group is completed. The value of the questions are often in the comparison of the different items and in having students think about what changes lead to what differences and why. • Problem solving items In these items (indicated by a pencil cluster logo), the intent is to have students work together to solve some small problem. After a few minutes, ask the groups to share their answers, vote on the different answers obtained, and have a discussion. A cylinder with a movable piston is filled with a uniform fluid. If the corks are all in equally tightly, which are most likely to pop when we hit the piston with a hammer? A. B. C. D. E. F. G. Cork 1 Corks 1 & 2 Cork 3 Cork 4 Some other combination All None 1 2 3 4 An object hung from a spring scale is lowered into water. When the object is immersed, the scale will read A. B. C. D. a larger value a smaller value the same value can’t tell – not enough info Consider the containers at right. Which of the following correctly compares the pressure (P) of the water at the bottoms of the containers? A. B. C. D. E. F. G. P1 = P2 = P3 P3 > P1 > P2 P3 > P1 = P2 P2 > P1 > P3 P1 = P2 > P3 P2 > P1 = P3 None of these (1) (2) (3) Consider the containers at right. Which of the following correctly compares the force (F) exerted by the water on the bottoms of the containers? A. B. C. D. E. F. G. F1 = F2 = F3 F3 > F1 > F2 F3 > F1 = F2 F2 > F1 > F3 F1 = F2 > F3 F2 > F1 = F3 None of these (1) (2) (3) Three cubes of equal volume are hung on strings. A and B have the same mass and block C has less. The blocks are lowered into a fish tank and they hang at rest as shown. How does the force exerted by the water on the top surface of cube A compare to the force exerted by the water on the top surface of cube B? A. The force on A is bigger B. The force on B is bigger C. They are the same. Three cubes of equal volume are hung on strings. A and B have the same mass and block C has less. The blocks are lowered into a fish tank and they hang at rest as shown. How do the buoyant forces exerted by the water on the three cubes rank? A. B. C. D. E. BFB > BFA = BFC BFB = BFA > BFC BFB > BFA > BFC BFA = BFB = BFC Some other ranking A. greater than B. less than C. the same as 10/28/11 13 A chunk of iron is sitting on a table. It is then moved from the table into a bucket of water sitting on the table. The iron now rests on the bottom of the bucket. The force the bucket exerts on the chunk when the block is sitting on the bottom of the bucket is __________the force that the table exerted on the chunk when the chunk was sitting on the table. Ph ysi cs 13 A. greater than B. less than C. the same as 10/28/11 14 A chunk of iron is sitting on a table. It is then moved from the table into a bucket of water sitting on the table. The iron now rests on the bottom of the bucket. The total force on the chunk when it is sitting on the bottom of the bucket is __________ it was on the table. Ph ysi cs 13 A. greater than B. less than C. the same as 10/28/11 15 A chunk of iron is sitting on a table. It is then covered by a bell jar which has a nozzle connected to a vacuum pump. The air is extracted from the bell jar. The force the table exerts on the block when the block is sitting in a vacuum is __________ the force that the table exerted on the block when the block was sitting in the air Ph ysi cs 13 A. greater than B. less than C. the same as 10/28/11 16 A chunk of iron is sitting on a scale. The iron and the scale are then both immersed in a large vat of water. After being immersed in the water, the scale reading will be __________ the scale reading when they were simply sitting in the air. (Assume the scale would read zero if nothing were sitting on it, even when it is under water.) Ph ysi cs 13 A ball floats in a beaker of water. The ball sinks in a beaker of mineral spirits. The mineral spirit will float above the water when poured slowly on top of water. If the ball is floating on the water 2/3 of the way under the water, what will happen to the ball when mineral spirits is slowly poured on top of the water? • Relative to the top of the water, A. The ball will go down. B. The ball will go up. C. The ball will stay at the same level. There is a lot of talk about the north polar ice cap melting. When it melts what will the result be on sea level? A. It will rise. B. It will fall. C. It will stay the same A large chunk of ice is floating in water in a bucket. When it melts what will the water level in the bucket do? A. It will rise. B. It will fall. C. It will stay the same Two identical glasses are filled to the same level with water. One of the two glasses has ice cubes floating in it. Which glass weighs more? A. The glass without ice cubes. B. The glass with ice cubes. C. The two weigh the same. D. There is not enough information to decide. Two identical glasses are filled to the same level with water. One of the two glasses has ice cubes floating in it. When the ice cubes melt, in which glass is the level of the water higher ? A. The glass without ice cubes. B. The glass with ice cubes. C. It is the same in both. D. There is not enough information to decide. Two balloons are connected by a pipe with a valve. When the valve is opened, what will happen? 1. The big balloon will get smaller and the small get larger until the two are equal. 2. The big balloon will get larger and the small get smaller until the small one is very small. 3. Something else will happen. Blood flows through a coronary artery that is partially blocked by deposits along the artery wall. Through which part of the artery is the flux (volume of blood per unit time) largest? A. The narrow part B. The wide part C. Same in both Blood flows through a coronary artery that is partially blocked by deposits along the artery wall. Through which part of the artery is the speed of the blood the largest? A. The narrow part B. The wide part C. Same in both You can readily observe that when you run water from a faucet at a moderate steady flow rate, the stream of water narrows as it descends. This implies that the speed of the water at point 2 is _______ the speed at point 1. Which best completes the sentence? A. greater than (>) B. less than (<) C. equal to (=) The main blood vessel carrying blood out of your heart is the aorta. It carries blood down towards the legs. In your abdomen it splits into two, the common iliac arteries. The diameter of a typical aorta is 2 cm, while the iliac arteries typically have diameters of about 1 cm. A typical value for the speed of the blood in the aorta is vA = 30 cm/s when the heart is contracting. While this is occurring, the speed of the blood flowing in the iliac arteries will be closest to A. B. C. D. E. F. 120 cm/s 60 cm/s 30 cm/s 15 cm/s 7.5 cm/s It’s not close to any of these. Smoking tobacco is bad for your circulatory health. In an attempt to maintain the blood’s capacity to deliver oxygen, the body increases its red blood cell production, and this increases the viscosity of the blood. In addition, nicotine from tobacco causes arteries to constrict. For a nonsmoker, with blood viscosity of 2.5 × 10–3 Pa·s, normal blood flow requires a pressure difference of 8.0 mm Hg between the two ends of a certain artery. If this person were to smoke regularly, his blood viscosity would increase to 2.8 × 10–3 Pa·s, and the diameter of his artery would constrict by 10%. Assuming the pressure difference has not changed, which of the two effects would have a larger effect on the amount of blood flow? A. B. C. D. E. The change in viscosity. The change in diameter. The effects of the two changes would be equal. Neither would have an effect on the flow. There is not enough information to tell Construct the two combinations of coffee straws as shown in the figure below. Fill your lungs with air and blow as hard as you can through each one. Which did you find? A. Arrangement A was faster. B. Arrangement B was faster. C. Both were the same. A. B.