Skills Worksheet Directed Reading A Section: Buoyancy and Density (pp. 412 419) 1. What is the upward force that fluids exert on all matter called? a. pascal force b. atmospheric pressure c. buoyant force d. density BUOYANT FORCE AND FLUID PRESSURE Use the terms from the following list to complete the sentences below. weight depth Archimedes principle 2. Pressure increases as increases. 3. The principle used to determine buoyant force is called. 4. The buoyant force is determined by the of the displaced water. WEIGHT VERSUS BUOYANT FORCE Use the terms from the following list to complete the sentences below. float sink 5. An object that weighs more than the buoyant force on it will 6. An object whose weight equals the buoyant force will. Sinking. 7. Which of the following is true when a rock sinks in water? a. Buoyant force is less than the rock s weight. b. Buoyant force equals the rock s weight. c. Buoyant force is greater than the rock s weight. d. There is no buoyant force on the rock. Holt California Physical Science 160 Forces in Fluids
Floating 8. Which of the following is true when a fish floats in water? a. Buoyant force is less than the fish s weight. b. Buoyant force equals the fish s weight. c. Buoyant force is greater than the fish s weight. d. There is no buoyant force on the fish. Buoying Up 9. Which of the following is true when a duck is buoyed up in water? a. Buoyant force is less than the duck s weight. b. Buoyant force equals the duck s weight. c. Buoyant force is greater than the duck s weight. d. There is no buoyant force on the duck. DENSITY AND FLOATING 10. What is density? a. mass per unit volume b. volume per unit mass c. weight per unit volume d. volume per unit weight 11. Why does a rock sink in water? a. The rock is denser than water. b. Water is denser than the rock. c. Air is denser than the rock. d. Water is less dense than air. More Dense Than Air 12. Why don t most substances float in air? a. Air is too dense. b. Most substances are denser than air. c. Air weighs too much. d. The volume of the atmosphere is too great. Less Dense Than Air 13. Which of the following is less dense than air? a. water b. ice c. helium d. a duck Holt California Physical Science 7 Forces in Fluids
DETERMINING DENSITY 14. What do you need to find an object s density? a. its pressure and volume b. its mass and volume c. its height and weight d. its weight and pressure Volume of a Regular Solid 15. How do you find the volume of a regular solid? a. Add the lengths of the sides. b. Multiply the lengths of the sides. c. Divide the lengths by 2. d. Measure the volume of air displaced. Volume of an Irregular Solid 16. How do you find the volume of an irregular solid? a. Add the lengths of the sides. b. Multiply the lengths of the sides. c. Divide the lengths by 2. d. Measure the volume of water displaced. CHANGING OVERALL DENSITY Changing the Shape 17. Which of the following features allows a ship to float? a. the ship s passengers b. the ship s shape c. the ship s hull d. the ship s material 18. Which of the following increases when steel is shaped into a hollow form? a. the steel s weight b. the steel s volume c. the steel s density d. the overall density Holt California Physical Science 8 Forces in Fluids
Changing the Mass Match the correct description with the correct term. Write the letter in the space provided. 19. air-filled ballast tanks 20. open ballast tanks 21. closed ballast tanks into which air is pumped a. diving submarine b. rising submarine c. floating submarine Changing the Volume 22. Which of the following is the organ that keeps some fish from sinking? a. gills b. swim bladder c. lungs d. brain Holt California Physical Science 9 Forces in Fluids
TEACHER RESOURCES Answer Key Directed Reading A SECTION: FLUIDS AND PRESSURE 1. fluid 2. liquids 3. move 4. increases 5. pressure 6. pascal 7. force 8. D 9. D 10. C 11. A 12. B 13. D 14. B 15. A 16. A 17. D 18. C 19. C 20. D 21. B 22. B 23. D 24. A 25. D SECTION: BUOYANCY AND DENSITY 1. C 2. depth 3. Archimedes principle 4. weight 5. sink 6. float 7. A 8. B 9. C 10. A 11. A 12. B 13. C 14. B 15. B 16. D 17. B 18. D 19. C 20. A 21. B 22. B Directed Reading B SECTION: FLUIDS AND PRESSURE 1. fluid 2. liquids and gases 3. They can move easily past each other. 4. Answers may vary. Sample answer: You pump in air particles that collide against each other and against the inside of the tire. The forces of the particles in these collisions creates pressure. 5. pressure 6. pressure 7. pascal 8. pascal 9. Answers may vary. Sample answer: The air inside the bubble exerts equal pressure in all directions, so the bubble expands equally in all directions and creates a round shape. 10. B 11. C 12. D 13. A 14. Answers may vary. Sample answer: The farther down you go through the atmosphere, the greater the pressure is. 15. 3 16. 4 17. 2 18. 5 19. 1 20. Answers may vary. Sample answer: The pressure on my eardrums changes as atmospheric pressure changes. The fluids in my body have to adjust to maintain equal pressure. 21. C 22. D 23. B 24. A 25. density Holt California Physical Science 107 Forces in Fluids