Q: A block is submerged in water and appears to weigh less than its actual weight. What is the apparent weight of the block equal to?

$$\text{Apparent weight} = \text{Weight out of water} - \text{Buoyant force}$$

Question 1

A brick is placed on a table in two different orientations, as shown in the first image. In which orientation does the brick exert a higher pressure on the table, and why?

Accepted Answer

When the brick is standing upright, because the force is distributed over a smaller area.

Question 2

A teacher lies unharmed on a bed of nails, as shown in the second image. Which physical principle explains why the teacher is not injured?

Accepted Answer

The force is spread over a large area, reducing the pressure on any single nail.

Question 3

Consider two bodies of water: a large but shallow lake (3 m deep) and a small but deep pond (6 m deep), as shown in the third image. At which location is the water pressure at the bottom greater, and why?

Accepted Answer

At the bottom of the deep pond, because pressure depends on depth, not volume.

Question 4

A water tower is shown in the fifth image. What factor primarily determines the water pressure at the base of the tower?

Accepted Answer

The height of the water column above the base.

Question 5

A cup with three holes at different depths is shown in the sixth image. Why does water spurt farther from the lowest hole?

Accepted Answer

Because the pressure increases with depth, causing water to exit faster.

Question 6

A stone is completely submerged in water, as shown in the ninth image. According to the displacement rule, what is true about the volume of water displaced?

Accepted Answer

It is equal to the volume of the stone.

Question 7

A block is submerged in water and appears to weigh less than its actual weight. What is the apparent weight of the block equal to?

Accepted Answer

$$	ext{Apparent weight} = 	ext{Weight out of water} - 	ext{Buoyant force}$$

Question 8

A fish expands its air bladder. What happens to its density and why?

Accepted Answer

Its density decreases because its volume increases while its mass stays the same.

Question 9

A submarine expels water from its ballast tanks while submerged. What happens to its density and why?

Accepted Answer

Its density decreases because it replaces water with air, making it more buoyant.

Question 10

Two solid blocks of identical size, one lead and one aluminum, are submerged in water. Upon which block is the buoyant force greater?

Accepted Answer

The buoyant force is the same on both blocks because they displace the same volume of water.

Question 11

A floating object displaces a weight of fluid equal to its own weight. This is an example of which principle?

Accepted Answer

Principle of flotation

Question 12

A ship floats higher in saltwater than in freshwater. Why?

Accepted Answer

Saltwater is denser, so less volume is needed to displace the ship's weight.

Question 13

According to Pascal's principle, what happens when pressure is applied to a confined fluid?

Accepted Answer

The pressure is transmitted undiminished to all parts of the fluid.

Question 14

In a hydraulic lift, a small force applied to a small piston lifts a much heavier car on a large piston. Which equation describes the relationship between the forces and areas?

Accepted Answer

$$\frac{F_1$}{A_1$} = \frac{F_2$}{A_2$}$$

Question 15

Which of the following is NOT possible in a hydraulic device?

Accepted Answer

The energy output exceeds the energy input.

Question 16

Surface tension causes water droplets to form spheres. What is the molecular explanation for this phenomenon?

Accepted Answer

Molecules at the surface are pulled inward by neighboring molecules, minimizing surface area.

Question 17

Which of the following will increase the capillary rise of a liquid in a tube?

Accepted Answer

Using a narrower tube.

Question 18

A paper clip can float on water due to surface tension. What would happen if soap is added to the water?

Accepted Answer

The paper clip would sink because soap reduces surface tension.

Question 19

Which of the following best describes why oil rises in a lamp wick?

Accepted Answer

Capillarity draws the oil upward through the narrow spaces in the wick.

Chapter 13: Liquids – Pressure, Buoyancy, and Surface Phenomena

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