Ground effect is felt at a height that is equal to the plane's wingspan. True or False

In a reversible process both the system and surrondings can be returned to their initial states. a)-True b)-False

Nuetrik [128]

Answer:

a)-True

Explanation:

When the direction of a process is reversed through infinitesimal changes to the system. The infinitesimal changes are done by the surroundings. After the process has been reversed the system and surroundings go back to their original state.

The changes take an infinite amount of time so, it is not possible practically.

6 0

3 years ago

A soil sample has a moist unit weight of 117 pcf, a moisture content of 17 percent, and soil particles with a specific gravity o

nikklg [1K]

Answer:

(A) Dry unit weight. = 15.71 kN/m³ =100.91 pcf

(B) Porosity = 40.82 %

(C) Degree of saturation = 66.52 %

(D) Weight of water, in pounds per cubic foot, to be added to reach full saturation = 81.22 pcf

Explanation:

(A) γd = $\frac{\gamma }{1+w}$ = $\frac{18.379}{1+.17} = 15.71$ KN/m³

(B) $\gamma _d =\frac{G_{s}* \gamma _w }{1+e}$ therefore $1+e = \frac{G_{s}* \gamma _w }{\gamma _d }$ $\frac{2.7*9.81}{15.71} =$ 1.69

Therefore e = 0.69 and

Porososity n = $\frac{e}{1+e}$ = $\frac{0.69}{1+0.69}$ × 100% = 40.82 %

(C) $S_{e} = w*G_{s}$ therefore S = $\frac{w*G_{s}}{e}$ = $\frac{0.17*9.81}{0.69}$ ×100 = 66.52 %

(D) $\gamma _{sat} =\frac{(G_{s}+e) \gamma_{w} }{1+e}$ = $\frac{(2.7+0.69)9.81}{1+0.69}$ = 19.68 kN/m³

The required amount of water is found from γ =ρ×g

ρ mass of water = $\frac{\gamma}{g} = \frac{(19.68-18.38)\frac{kN}{m^{3} } }{9.81 kg\frac{m}{s^{2} } } *\frac{1000 N}{kN} *\frac{9.81 kg\frac{m}{s^{2} } }{N} = 1301 \frac{kg}{m^{3} }$

1 kg/m³ = 0.062 pcf therefore 1301 kg/m³ = 1301 ×0.062 pcf or 81.22 pcf

6 0

3 years ago

A 4-pole, 3-phase induction motor operates from a supply whose frequency is 60 Hz. calculate: 1- the speed at which the magnetic

DiKsa [7]

Answer:

The answer is below

Explanation:

1) The synchronous speed of an induction motor is the speed of the magnetic field of the stator. It is given by:

$n_s=\frac{120f_s}{p}\\ Where\ p\ is \ the \ number\ of\ machine\ pole, f_s\ is\ the\ supply \ frequency\\and\ n_s\ is \ the \ synchronous\ speed(speed \ of\ stator\ magnetic \ field)\\Given: f_s=60\ Hz, p=4. Therefore\\\\n_s=\frac{120*60}{4}=1800\ rpm$

2) The speed of the rotor is the motor speed. The slip is given by:

$Slip=\frac{n_s-n_m}{n_s}. \\ n_m\ is\ the \ motor\ speed(rotor\ speed)\\Slip = 0.05, n_s= 1800\ rpm\\ \\0.05=\frac{1800-n_m}{1800}\\\\ 1800-n_m=90\\\\n_m=1800-90=1710\ rpm$

3) The frequency of the rotor is given as:

$f_r=slip*f_s\\f_r=0.04*60=2.4\ Hz$

4) At standstill, the speed of the motor is 0, therefore the slip is 1.

The frequency of the rotor is given as:

$f_r=slip*f_s\\f_r=1*60=60\ Hz$

6 0

4 years ago

The distillation column in Figure 3 is set up for so-called boil-up (V) control. It has

11111nata11111 [884]

A distillation column is an essential item used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on the differences in volatilities. Fractionating columns are used in small scale laboratory distillations as well as large scale industrial distillations.

3 0

3 years ago

Engine horsepower decreases ________% for every___________feet above sea level.

Nitella [24]

Answer:

Engine horsepower decreases 3.5% for every 1,000 feet above sea level.

4 0

3 years ago