Question 1

A rock suspended by a string weighs 5 N out of water and 3 N when submerged. What is the buoyant force on the rock?

Accepted Answer

The buoyant force is the difference between the weight of the rock in air and its apparent weight when submerged, which is 5 N - 3 N = 2 N.

Question 2

The density of a submerged submarine is about the same as the density of

Accepted Answer

A submerged submarine adjusts its density to be roughly equal to the water around it to maintain neutral buoyancy, allowing it to stay at a constant depth without sinking or floating.

Question 3

When holes are drilled through the wall of a water tower , water will spurt out the greatest horizontal distance from the hole closest to

Accepted Answer

The water pressure is greatest at the bottom of the tower due to the weight of the water above, causing water to spurt out the farthest from a hole at the bottom.

Question 4

When an ice cube in a glass of water melts, the water level

Accepted Answer

When an ice cube melts in water, the water level remains the same because the volume of water displaced by the ice is equal to the volume of water the ice turns into when it melts.

Question 5

A one-ton blimp hovers in the air. The buoyant force acting on it is

Accepted Answer

The buoyant force must equal the weight of the blimp (one ton) for it to hover in equilibrium.

Question 6

A scale from which a rock is suspended reads 5 N when the rock is out of water and 3 N when the rock is submerged. The density of the rock is

Accepted Answer

The buoyant force is 2 N (5 N - 3 N), which equals the weight of the water displaced. The weight of the rock is 5 N. The density of the rock is the weight of the rock divided by the buoyant force, which is 5 N / 2 N = 2.5 times the density of water.

Question 7

A swimmer cannot use a long hose to snorkel more than a meter deep because air

Accepted Answer

The correct answer is D because as a swimmer goes deeper, the pressure of the water increases. This increased pressure compresses the air in the lungs, making it harder to inhale air from the surface through a long hose. The pressure difference between the surface air and the higher-pressure environment in the lungs prevents air from freely entering the lungs, making it difficult to breathe.

Question 8

The mass of a cubic meter of water is

Accepted Answer

The mass of a cubic meter of water is approximately 1000 kg, as 1 cubic meter of water is defined to have a mass of 1000 kilograms at 4 degrees Celsius.

Question 9

Compared to the buoyant force of the atmosphere on a 1-liter helium-filled balloon, the buoyant force of the atmosphere on a nearby 1-liter solid iron block is

Accepted Answer

The buoyant force exerted by a fluid (in this case, the atmosphere) on an object depends only on the volume of the fluid displaced by the object, not on the object's content or weight. Since both the helium-filled balloon and the solid iron block displace the same volume of air (1 liter), the buoyant force on both is the same.

Question 10

A suction cup sticks to a wall. It is

Accepted Answer

The answer of A suction cup sticks to a wall....

Question 11

A balloon is buoyed up with a force equal to the

Accepted Answer

A balloon is buoyed up by a force equal to the weight of the air it displaces, according to Archimedes' principle. This principle states that any object, totally or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.

Question 12

Three icebergs are each floating in bathtubs filled to the brim with water. Iceberg A has large air bubbles in it. Iceberg B has unfrozen water in it. Iceberg C has an iron railroad spike in it. When the ice melts, what happens?

Accepted Answer

The water level in C decreases because the iron spike displaces more water due to its higher density compared to ice, so when the ice melts, the overall water level drops. Icebergs A and B's water levels remain the same due to the principle of displacement: the volume of water displaced by the iceberg is equal to the volume of water it adds when melted, regardless of air bubbles or unfrozen water inside.

Question 13

The pressure in a liquid depends on liquid

Accepted Answer

The pressure in a liquid depends on both the depth of the liquid and the density of the liquid. The deeper you go in a liquid, the greater the pressure because there is more weight of the liquid above pushing down. Similarly, a denser liquid exerts more pressure than a less dense liquid at the same depth because there is more mass in a given volume. This is described by the formula P = ρgh, where P is the pressure, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the depth of the liquid.

Question 14

A heavy glass ball is placed in a pie pan that floats in a bucket. The water level at the side of the bucket is marked. Then the glass ball is removed and allowed to sink in the bucket. The water line at the side of the bucket is now

Accepted Answer

When the glass ball is in the pie pan, it displaces a volume of water equal to its weight. When the ball is removed and sinks, it displaces a volume of water equal to its volume, which is less than the volume displaced when it was floating. Therefore, the water level is lower.

Question 15

A hydraulic press multiplies a force by 100. This multiplication is done at the expense of

Accepted Answer

The principle of a hydraulic press is based on Pascal's law, which states that when pressure is applied to a confined fluid, the pressure change occurs throughout the entire fluid. Thus, to conserve energy, if a hydraulic press multiplies the force applied to it, the distance through which the force acts must be reduced accordingly. This is because the work done (force × distance) remains constant, assuming no losses in the system.

Question 16

The pressure at the bottom of a jug filled with water does NOT depend on

Accepted Answer

The pressure at the bottom of a jug filled with water depends on the height of the liquid, the acceleration due to gravity, and the density of the water, but not on the surface area of the water.

Question 17

If a strong wind from the west breaks a window in the north wall of a house, most of the glass will fall

Accepted Answer

The answer of If a strong wind from the west...

Question 18

Buoyant force is greatest on a submerged

Accepted Answer

The buoyant force is equal to the weight of the fluid displaced by the object. Since aluminum has a lower density than lead, a 1-kg block of aluminum will displace more fluid than a 1-kg block of lead. Therefore, the buoyant force on the aluminum block will be greater than the buoyant force on the lead block.

Question 19

The buoyant force on a rock is least when the rock is submerged

Accepted Answer

The buoyant force on an object submerged in a fluid depends on the volume of fluid displaced by the object, not its depth. Therefore, the buoyant force on the rock remains constant regardless of whether it is near the bottom, near the surface, or halfway to the bottom.

Question 20

Gas pressure inside an inflated stretched balloon is actually

Accepted Answer

The gas pressure inside an inflated stretched balloon is greater than the air pressure outside due to the elastic force of the balloon's material trying to contract, which increases the pressure of the gas inside.

Quiz 7: Fluid Mechanics