In lab you find that a 1-kg rock suspended above water weighs $10 \mathrm{~N}$. When the rock is suspended beneath the surface of the water, the scale reads $8 \mathrm{~N}$. a. What is the buoyant force on the rock? b. If the container of water weighs $10 \mathrm{~N}$ on the weighing scale, what is the scale reading when the rock is suspended beneath the surface of the water? c. What is the scale reading when the rock is released and rests at the bottom of the container?

A 12-kg piece of metal displaces 2 L of water when submerged. Show that its density is 6000 kg/m3. How does this compare with the density of water?

A dike in Holland springs a leak through a hole of area $1 \mathrm{~cm}^2$ at a depth of $2 \mathrm{~m}$ below the water surface. How much force must a boy apply to the hole with his thumb to stop the leak? Could he do it?

A 1-m-tall barrel is closed on top except for a thin pipe extending $5 \mathrm{~m}$ up from the top. When the barrel is filled with water up to the base of the pipe (1 meter deep), the water pressure on the bottom of the barrel is $10 \mathrm{kPa}$. What is the pressure on the bottom when water is added to fill the pipe to its top?

If you swim beneath the surface in saltwater, will the pressure be greater than in fresh water at the same depth?

Why does the density of a liquid not undergo much of a change as we go to lower depths?

A $12-\mathrm{kg}$ piece of metal displaces $2 \mathrm{~L}$ of water when submerged. Show that its density is $6000 \mathrm{~kg} / \mathrm{m}^3$. How does this compare with the density of water?

Suppose that you balance a $5-\mathrm{kg}$ ball on the tip of your finger, which has an area of $1 \mathrm{~cm}^2$. Show that the pressure on your finger is $50 \mathrm{~N} / \mathrm{cm}^2$, which is $500 \mathrm{kPa}$

Calculate the average force per nail when Sara, who weighs 120 pounds, lies on a bed of nails and is supported by 600 nails.

If you use a batch of cake batter for cupcakes and bake them for the time suggested for baking a cake, what will be the result?

The top floor of a building is $20 \mathrm{~m}$ above the basement. Show that the water pressure in the basement is nearly $200 \mathrm{kPa}$ greater than the water pressure on the top floor.

A particular atom contains 29 electrons, 34 neutrons, and 29 protons. What is the identity of this element, and what is its atomic number?

Show that the water pressure at the bottom of the 50 -m-high water tower in the chapter-opening photo is $500,000 \mathrm{~N} / \mathrm{m}^2$, which is approximately $500 \mathrm{kPa}$

The depth of water behind the Hoover Dam is $220 \mathrm{~m}$. Show that the water pressure at the base of this dam is $2200 \mathrm{kPa}$