Question 1

A block of wood floats in water with 60% of its volume submerged. If the density of water is $$1000\ \mathrm{kg/m^3$}$$, what is the density of the wood?

Accepted Answer

$$600\ \mathrm{kg/m^3$}$$

Question 2

Which of the following best describes the physical meaning of the buoyant force according to Archimedes’ Principle?

Accepted Answer

It is equal to the weight of the fluid displaced by the object.

Question 3

A sealed container is filled with water and a block is fully submerged in it. If the block is held at rest by a string, what is the tension in the string?

Accepted Answer

The tension equals the weight of the block minus the buoyant force.

Question 4

A beaker containing water is placed on a scale. A hollow box floats in the water. What happens to the reading on the scale when the box is added?

Accepted Answer

The reading increases by the weight of the box.

Question 5

Which equation expresses the pressure at a depth $$h in a $$fluid of density $$\rho$$ under gravity $$g$$?

Accepted Answer

$$P = P_0$ + \rho g h$$

Question 6

A hurricane causes a region of low pressure above the ocean surface. According to Bernoulli’s equation, what happens to the speed of the air in this region?

Accepted Answer

The speed of the air increases.

Question 7

The Wright Flyer’s wings generate lift due to the difference in air pressure above and below the wing. Which principle explains this phenomenon?

Accepted Answer

Bernoulli’s Principle

Question 8

Water flows through a pipe that narrows from area $$A_1 to$$ $$A_2. If $$the velocity in the wide section is $$v_1$$, what is the velocity $$v_2 in $$the narrow section according to the continuity equation?

Accepted Answer

$$v_2$$ = \dfrac{$$A_1$$}{$$A_2$$} $$v_1$$

Question 9

A fluid flows horizontally through a pipe. At point 1, the pressure is $$P_1$$ and the speed is $$v_1. At $$point 2, the pressure is $$P_2$$ and the speed is $$v_2. $$Which equation relates these quantities according to Bernoulli’s equation?

Accepted Answer

$$P_1$$ + \dfrac{1}{2} \rho $$v_1^2$$ = $$P_2$$ + \dfrac{1}{2} \rho $$v_2^2$

Question 10

A hot air balloon floats because the air inside is less dense than the air outside. Which principle is responsible for the upward force on the balloon?

Accepted Answer

Archimedes’ Principle

Question 11

A submarine is submerged in seawater. If the density of seawater is $$1025\ \mathrm{kg/m^3$}$$ and the submarine displaces $$500\ \mathrm{m^3$} of $$water, what is the buoyant force acting on it? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$5,022,500\ \mathrm{N}$$

Question 12

A fluid flows upward through a vertical pipe. At the bottom, the pressure is $$P_1$$ and the height is $$h_1. At $$the top, the pressure is $$P_2$$ and the height is $$h_2. $$Which form of Bernoulli’s equation applies?

Accepted Answer

$$P_1$$ + \rho g $$h_1$$ + \dfrac{1}{2} \rho $$v_1^2$$ = $$P_2$$ + \rho g $$h_2$$ + \dfrac{1}{2} \rho $$v_2^2$

Question 13

A sealed syringe is filled with water. If you push on the plunger, the pressure increases everywhere inside the syringe. Which principle explains this?

Accepted Answer

Pascal’s Principle

Question 14

A river narrows and the water flows faster in the narrow region. What happens to the pressure in the fast-flowing region according to Bernoulli’s equation?

Accepted Answer

The pressure decreases.

Question 15

A log floats in water. If you push the log completely underwater and then release it, what will happen?

Accepted Answer

The log will rise to the surface and float.

Question 16

An airplane wing is designed so that air moves faster over the top than the bottom. According to Bernoulli’s principle, what is the result?

Accepted Answer

Lower pressure above the wing, creating lift.

Question 17

A box is floating in a beaker of water. If you add more water to the beaker, what happens to the buoyant force on the box?

Accepted Answer

The buoyant force remains the same.

Question 18

A fluid flows through a horizontal pipe with varying diameter. If the flow rate is $$Q$$, which equation relates the flow rate to the area $$A$$ and velocity $$v$$?

Accepted Answer

$$Q = A v$$

Question 19

A diver descends to a depth of $$20\ \mathrm{m} in $$seawater ($$\rho = 1025\ \mathrm{kg/m^3$}). $$What is the gauge pressure at this depth? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$201,850\ \mathrm{Pa}$$

Fluid Statics and Dynamics: Principles, Equations, and Applications

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