/
Fluid Mechanics Essentials
Save to my account
Sign up
Fluid Mechanics Essentials
Fluid Mechanics Essentials
Study
1
Question
What is fluid mechanics?
Page 1
Answer
The branch of physics that studies how fluids move and how they interact with forces.
2
Question
What defines a fluid?
Page 1
Answer
Any substance that flows and takes the shape of its container.
3
Question
How do liquids and gases differ as fluids?
Page 1
Answer
Liquids have definite volume but no fixed shape; gases have no fixed shape or volume.
4
Question
What is density in the context of fluids?
Page 1
Answer
The mass per unit volume of a substance, with SI unit kg/m³.
5
Question
What determines whether an object sinks or floats in a fluid?
Page 1
Answer
Objects denser than the fluid sink; less dense objects float.
6
Question
What is the approximate density of water (freshwater, near 4°C)?
Page 1
Answer
About 1000 kg/m³.
7
Question
What is specific gravity?
Page 1
Answer
The ratio of a substance’s density to the density of a reference substance.
8
Question
How does specific gravity determine if an object sinks or floats in water?
Page 1
Answer
SG > 1 means it sinks (denser than water); SG < 1 means it floats (less dense than water).
9
Question
What is the definition of pressure?
Page 1
Answer
The force applied perpendicular to a surface per unit area; fluids exert it in all directions.
10
Question
What is the SI unit of pressure?
Page 1
Answer
Pascal (Pa), where 1 Pa = 1 N/m².
11
Question
Calculate the pressure from a force of 200 N applied evenly over 0.50 m².
Page 2
Answer
$P = \frac{F}{A} = \frac{200}{0.50} = 400$ Pa.
12
Question
What force acts on a 0.20 m² area at a pressure of 2.50 kPa?
Page 2
Answer
$F = P \times A = 2.50 \times 10^{3} \times 0.20 = 500$ N.
13
Question
What is the contact area for a 15 kN force at 120 kPa in a hydraulic ram?
Page 2
Answer
$A = \frac{F}{P} = \frac{15{,}000}{120{,}000} = 0.125$ m².
14
Question
How is absolute pressure calculated from gauge and atmospheric pressure?
Page 2
Answer
$P_{abs} = P_{gauge} + P_{atm}$ (absolute is always positive).
15
Question
What is the hydrostatic pressure increase with depth (gauge pressure) in a fluid?
Page 2
Answer
$\Delta P = \rho g h$ (pressure increase with depth due to fluid weight).
16
Question
What hydrostatic (gauge) pressure acts on a diver at 3 m depth in water?
Page 2
Answer
$\Delta P = \rho g h = 1000 \times 9.8 \times 3 = 29{,}400$ Pa (about 29.4 kPa).
17
Question
What is Pascal's principle?
Page 2
Answer
External pressure applied on a confined liquid is transmitted evenly in all directions.
18
Question
What equation expresses Pascal's principle for a hydraulic system?
Page 3
Answer
$\dfrac{F_1}{A_1} = \dfrac{F_2}{A_2}$ (pressure is transmitted equally in a confined fluid).
19
Question
What is Archimedes’ principle?
Page 3
Answer
The buoyant force (upthrust) equals the weight of the displaced fluid.
20
Question
What is the formula for buoyant force (Archimedes’ principle)?
Page 3
Answer
$F_b = \rho g V_{\text{displaced}}$, where $V_{\text{displaced}}$ is the volume of displaced fluid.
21
Question
What buoyant force acts on a fully submerged 5-liter container in water?
Page 3
Answer
$V = 0.005$ m³, $F_b = 1000 \times 9.8 \times 0.005 = 49$ N.
22
Question
What is the continuity equation for incompressible flow?
Page 3
Answer
$A_1 v_1 = A_2 v_2$ (volume flow rate is constant).
23
Question
What is the continuity equation for compressible flow?
Page 3
Answer
$\rho_1 A_1 v_1 = \rho_2 A_2 v_2$ (mass flow rate is constant).
24
Question
Under Bernoulli’s principle (steady, incompressible, nonviscous flow along a streamline), how are fluid speed and pressure related?
Page 3
Answer
Higher flow speed corresponds to lower static pressure; lower speed corresponds to higher static pressure (all else equal).
25
Question
What is the Bernoulli equation (along a streamline for steady, incompressible, nonviscous flow)?
Page 3
Answer
$P + \frac{1}{2}\rho v^2 + \rho g h = \text{constant}$ (total mechanical energy per unit volume).
26
Question
If absolute pressure is 250 kPa and atmospheric pressure is 100 kPa, what is the gauge pressure?
Page 2
Answer
$P_{gauge} = P_{abs} - P_{atm} = 250 - 100 = 150$ kPa.