Critical Thinking
Applying Concepts In order to save someone who has fallen through the ice of a frozen lake, rescuers often reach the victim by crawling across the ice on their stomachs. Explain why the rescuers use this technique.
Designing an Experiment Your lab has two pressurized gas cylinders, each containing a different gas. Describe an experiment that could be used to determine whether each gas is less dense than air.
Applying Concepts For patients with muscles weakened due to injury, physical therapists recommend exercising in a swimming pool. Why is pool exercise preferred to exercise in a gym?
Using Models The high-speed winds of a hurricane sometimes cause houses to explode. Use a drawing to model the pressures acting on the house. Explain the areas of high and low pressure using Bernoulli's principle.
Math Skills
Use the illustration to answer Questions 24 and 25. The results of adding a small stone to a beaker that was filled to the brim with water is shown below.
Converting Units What is the volume of the stone in cm3? (Hint: 1.0 mL = 1.0 cm3)
Calculating If 1.0 cm3 equals 1.0 mL, and 1.0 cm3 of water has a mass of 1.0 g, calculate the buoyant force acting on the stone.
Using Formulas A 520-N ballet dancer is balanced on the toe of her shoe. If the toe has an area of 0.0010 m2, what pressure does she exert on the floor?
Using Formulas A small hydraulic jack exerts a force of 2200 N. If the area of the jack's output piston is 0.0060 m2, what is the pressure of the hydraulic fluid inside the jack?
Concepts in Action
Comparing and Contrasting Water exerts pressure on all sides of a submerged submarine. Compare and contrast the pressures acting on the submarine at a depth of 50 m to the pressures at a depth of 200 m.
Predicting An empty metal can is capped, attached to weights, and thrown into a deep ocean trench. A second, identical metal can is left uncapped, attached to weights, and thrown into the same trench. Both cans sink. Predict what will happen to each can and explain your reasons.
Applying Concepts When a driver presses on the brake pedal of a car, the car is easily brought to a stop. Explain how the car's hydraulic braking system transmits and increases the force applied to the brake pedal.
Writing in Science Explain how airplane wings and the wings of birds affect the air flowing over them to produce lift.
Performance-Based Assessment
Using Models Use what you have learned from this chapter to make a model boat out of a 10-cm-square piece of foil. Test your model boat in a tank of water to see how many pennies it can support before sinking. Compare the performance of your boat with those of your classmates. Suggest several design improvements based on your results.
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