Chapter 13
In answering the question why bodies float higher in saltwater than in freshwater your friend replies that the reason is that saltwater is denser than freshwater. How would you answer the same question?
A body floats higher in denser fluid because it does not have to sink as far to displace a weight of fluid equal to its own weight. A smaller volume of the displaced denser fluid is able to match the weight of the floating body.
Which do you suppose exerts more pressure on the ground - a 5000-kg elephant or a 50-kg lady standing on spike heels? (Which will be more likely to make dents in a linoleum floor?)
A woman with spiked heels exerts considerably more pressure on the ground than an elephant.
How does water pressure 1 m beneath the surface of a lake compare with water pressure 1 m beneath he surface of a swimming pool.
Both are the same, pressure depends on depth.
A block of aluminum with a volume of 10cm3 is placed in a beaker of water filled to the brim. Water overflows. The same is done in another beaker with a 10cm3 block of lead. Does the lead displace more, less, or the same amount of water?
Both blocks have the same volume and therefore displace the same amount of water.
Which teapot holds more liquid?
Both teapots hold the same amount of liquid
Why does water seek its own level?
Consequence of pressure depending on depth.
Why is it inaccurate to say that heavy objects sink and that light objects float.
Heavy objects may or may not sink depending on their densities. A heavy log floats while a small rock sinks.
The relative densities of water, ice, and alcohol are 1.0, 0.9, and 0.8, respectively. do ice cubes float higher or lower in a mixed alcoholic drink? what comment can you make about a cocktail in which the ice cubes lie submerged at the bottom of the glass?
Ice cubes will float lower in a mixed drink because the mixture of alcohol and water is less dense than water. in a less dense liquid a greater volume of liquid must be displaced to equal the weight of the floating ice. In pure alcohol, the volume of alcohol equal to that of the ice cubes weighs less than the ice cubes, and buoyancy is less than weight and ice cubes will sink. submerged ice cubes in a cocktail indicate that it is predominantly alcohol.
You know that a sharp knife cuts better than a dull knife. Do you know why this is so?
It has a thinner cutting area which results in more cutting pressure for a given force.
if water faucets upstairs and downstairs are turned fully on, will more water per second flow out of the upstairs faucets or downstairs?
More water will flow from a downstairs open faucet because of the greater pressure since pressure depends on depth. The downstairs faucet is effectively deeper than the upstairs faucet.
When you are standing, blood pressure in your legs is greater than in your upper body. Would this be true for an astronaut in orbit?
No, in orbit where support is absent, there are no pressure differences due to gravity.
Which is more likely to hurt - being stepped on by a 200 lb man wearing loafers or being stepped on by a 100 lb woman wearing heels.
Pressure would be appreciably greater by the woman which would hurt more.
Why is it elevated? Why are the hoops closer together near the bottom part of the tank?
Produce suitable water pressure in the faucets. The water pressure is greater at the bottom.
A block of aluminum with a mass of 1 kg is placed in a beaker of water filled to the brim. Water overflows. The same is done in another beaker with a 1 kg block of lead. Does the lead displace more less or the same amount of water.
The aluminum displaces more water.
a piece of iron placed on a block of wood makes it float lower in the water. if the iron were instead suspended beneath the wood, would the wood float as low, lower, or higher? defend your answer
The block of wood would float higher. Law of flotation allows the iron and wood unit displaces its combined weight and the same volume of water whether the iron is on top or bottom.
Why does an inflated beach ball pushed beneath the surface of water swiftly shoot above the water surface when released.
The buoyant force on the beach ball beneath the surface is much greater than the force of gravity on the ball producing a large upward force and large accleration.
will a rock gain or lose buoyant force as it sinks deeper in water? or will the buoyant force remain the same at greater depths? defend your answer
The buoyant force will remain unchanged on the sinking rock because it displaces the same volume and weight of water at any depth.
when the wooden block is placed in the beaker, what happens to the scale reading? answer the same question for an iron block
The total weight on the scale is the same either way.
What concept is being demonstrated in the picture and why is he careful that the broken pieces are small and numerous.
The concept of pressure is being demonstrated. He is careful so that his weight is applied over a large contact area then the sharp glass provides insufficient pressure to cut the feet.
A can of diet soda floats in water whereas a can of regular soda sinks. Explain this phenomenon first in terms of density, then in terms of weight versus buoyant force.
The diet is less dense than water whereas the regular drink is denser than water. The weight of the can is less than the buoyant force that would act on it if totally submerged. So it floats when the buoyant force equals the weight of the can.
The density of a rock doesn't change when it is submerged in water, but your density changes when you are submerged.
The higher pressure at lower depth compresses our body in contrast to a rock which cannot be compressed.
A barge filled with scrap iron is in a canal lock. If he iron is thrown overboard, does the water level at the side of the lock rise fall or remain unchanged.
The water level will fall. This is because the iron will displace a greater amount of water while being supported than when being submerged. A floating object displaces its weight of water which is more than its own volume.
Suppose that you wish to lay a level foundation for a home on hilly and bush terrain. How can you use a garden hose filled with water to determine equal elevations for distant points?
The water surface at one end of the hose will be at the same elevation above sea level as the water surface at the other end of the hose.
Why are persons who are confined to bed less likely to develop bedsores on their bodies if they rest on a water bed rather than an ordinary mattress.
There is less pressure in the water bed due to the greater contact area.
What common liquid covers more than two thirds of our planet, makes up 60% of our bodies and sustains our lives and lifestyles in countless ways?
Water
Why does your body get more rest when you're lying down than when you're sitting? Is blood pressure in your legs greater?
When lying the heart does not have to pump blood to the heights that correspond to standing or sitting.
why will a volleyball held beneath the surface of water have more buoyant force than if it's floating?
When the ball is beneath the surface it displaces a greater weight of water.
Why is blood pressure measured in the upper arm, at the elevation of your heart?
Your upper arm is at the same level as your heart so the blood pressure in your upper arm will be the same as the blood pressure in your heart.
