Exam 1

Question 1

Definition of a fluid

Answer 1

A substance that deforms continuously when acted upon by a shearing stress of any magnitude (i.e., they will flow).

Question 2

g

Answer 2

9.8 m/s^2; 32.2 ft/s^2

Question 3

Deg R

Answer 3

deg R = deg F + 459.67

Question 4

1 lb

Answer 4

1 lb = (1 slug) (1 ft/s^2)

Question 5

Weight (W)

Answer 5

W = mg

Question 6

1 N

Answer 6

1 kg *m/s^2

Question 7

1 watt (W)

Answer 7

1 W = 1 J/s

Question 8

1 J (joule)

Answer 8

1 J = 1 N * m

Question 9

1 Pa

Answer 9

1 N/m^2

Question 10

sea-level atmospheric pressure

Answer 10

14.7 psi

101 kPa

Question 11

specific mass

Answer 11

density (rho) = mass/volume

Question 12

specific weight

Answer 12

(gamma) = rho * g

Question 13

specific gravity

Answer 13

SG =rho/rho_water

= gamma/gamma_water

Question 14

shear stress

Answer 14

(tau) = mu* du/dy,
where mu = viscosity
du/dy = velocity gradient

Question 15

Newtonian fluids

Answer 15

shearing stress is linearly related to the rate of shearing strain (velocity gradient);
i.e., tau vs du/dy is linear

Question 16

no-slip condition

Answer 16

fluid “sticks” to a surface (U=0)

Question 17

direction of shear stress on a surface

Answer 17

same direction as velocity

Question 18

Reynold’s number

Answer 18

ratio of inertia to viscous forces. dimensionless.

Re = (fluid density*average velocity * characteristic length)/mu

Question 19

Bulk modulus

Answer 19

A property used to describe compressibility
Ev= -dp/(dV/V) or dp/(drho/rho)
where dp is the differential change in pressure needed to create a differential change in volume (dv) of a volume (V)
(negative sign is because an increase in pressure will cause a decrease in volume)

Question 20

Large values for the bulk modulus indicate that the fluid is…

Answer 20

relatively incompressible (i.e. it takes a large change in pressure to create a small change in volume).

Question 21

When does boiling occur?

Answer 21

When the absolute pressure within a fluid reaches the vapor pressure.

Question 22

Surface tension

Answer 22

the intensity of molecular attraction per unit length along any line in the surface

Question 23

The value of surface tension _____ as temperature increases.

Answer 23

decreases

Question 24

Definition of pressure

Answer 24

Normal force per unit area

Question 25

Pascal’s law

Answer 25

The pressure at a point in a fluid at rest, or in motion, is independent of direction as long as there are no shearing stresses present.

Question 26

What is a surface force, and what are the 2 types

Answer 26

Force proportional to the area. 
Normal force (pressure force sigma or P)
Tangent force (shear stress force tau)

Question 27

What is a body force?

Answer 27

Force proportional to the volume (weight = gamma * volume)

Question 28

pressure variations for a fluid

Answer 28

pressure does not change in x direction (dp/dx=0)
pressure does not change in y direction (dp/dx=0)
pressure is a function of gamma in z direction (dp/dz=-gamma).

Question 29

in an incompressible fluid: moving upwards, pressure ____.

Answer 29

decreases.

Question 30

moving downwards, pressure ____.

Answer 30

increases

Question 31

moving horizontally, pressure ______.

Answer 31

does not change.

Question 32

kinematic viscosity

Answer 32

= dynamic viscosity (mu)/density

Question 33

speed of sound

Answer 33

= sqrt(Ev/rho)

speed of sound in solids > liquids> gases