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3 years ago

An HVAC contracting company sent out three work crews to complete three

Engineering

1 answer:

Doss [256]3 years ago

6 0

Answer: 156 hours

Explanation:

Crew One worked 10-, 9-, 11-, 12-, and 9-hours for the week. The total hours worked by Crew One will be:

= 10 + 9 + 11 + 12 + 9

= 51 hours.

Crew Two worked 9, 12, 12, 9 and 9 hours. The total hours worked by Crew Two for the week will be:

= 9 + 12 + 12 + 9 + 9

= 51 hours

Crew Three worked 12-, 12-, 10-, 9-, and 11-hour daily. The total hours worked by Crew Three for the week will be:

= 12 + 12 + 10 + 9 + 11

= 54 hours

The total hours worked by the three crews for the week will be:

= 51 hours + 51 hours + 54 hours

= 156 hours

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The current entering the positive terminal of a device is i(t)= 6e^-2t mA and the voltage across the device is v(t)= 10di/dtV.

liberstina [14]

Answer:

a) 2,945 mC

b) P(t) = -720*e^(-4t) uW

c) -180 uJ

Explanation:

Given:

i (t) = 6*e^(-2*t)

v (t) = 10*di / dt

Find:

( a) Find the charge delivered to the device between t=0 and t=2 s.

( b) Calculate the power absorbed.

( c) Determine the energy absorbed in 3 s.

Solution:

- The amount of charge Q delivered can be determined by:

dQ = i(t) . dt

$Q = \int\limits^2_0 {i(t)} \, dt = \int\limits^2_0 {6*e^(-2t)} \, dt = 6*\int\limits^2_0 {e^(-2t)} \, dt$

- Integrate and evaluate the on the interval:

$= 6 * (-0.5)*e^-2t = - 3*( 1 / e^4 - 1) = 2.945 C$

- The power can be calculated by using v(t) and i(t) as follows:

v(t) = 10* di / dt = 10*d(6*e^(-2*t)) /dt

v(t) = 10*(-12*e^(-2*t)) = -120*e^-2*t mV

P(t) = v(t)*i(t) = (-120*e^-2*t) * 6*e^(-2*t)

P(t) = -720*e^(-4t) uW

- The amount of energy W absorbed can be evaluated using P(t) as follows:

$W = \int\limits^3_0 {P(t)} \, dt = \int\limits^2_0 {-720*e^(-4t)} \, dt = -720*\int\limits^2_0 {e^(-4t)} \, dt$

- Integrate and evaluate the on the interval:

$W = -180*e^-4t = - 180*( 1 / e^12 - 1) = -180uJ$

6 0

4 years ago

Consider a flat plate that is 25 mm long, 30 mm wide, and 1 mm thick and a 50 mm long cylinder with the same volume as the plate

Blizzard [7]

Answer:

Average heat transfer =42.448w/m^2k

Nud = 13.45978

Explanation:

See attachment for step by step guide

4 0

3 years ago

Truth table for (A+B)(B+C)

serg [7]

Answer:

A truth table is a logical expression of the given inputs specially in boolean algebra and boolean functions in computer science and digital electronics.

Explanation:

Number of variables are 3 i.e A,B and C

so the number of bits are 2^3=8

A B C A+B B+C (A+B)(B+C)

0 0 0 0 0 0

0 0 1 0 1 0

0 1 0 1 1 1

0 1 1 1 1 1

1 0 0 1 0 0

1 0 1 1 1 1

1 1 0 1 1 1

1 1 1 1 1 1

5 0

3 years ago

Explain the difference between the connection of a cumulative compound and a differential compound motor

Alexandra [31]

Answer:

Explanation:

A motor is a device that directs current in electrical energy form to mechanical energy, which is known as direct current (DC) motors.

DC motors are of three types: (a) The series motor, (b) The shunt motor, and (c) the compound motor. Our main focus here is the Compound motor, which is further sub-divided into:

i) The cumulative compound motors

ii) The differential compound motors

The difference between these two are:

Cumulative compound motors Differential compound motors

In cumulative compound motors, In differential compound motors,

both the series and shunt windings both series and shunt are

are connected in a way that, connected in a way that the

production of fluxes through them production of fluxes via them

assist each other i.e. they aid each always opposes each other i.e.

other in the production of magnetism they oppose each other in the

production of magnetism.

6 0

3 years ago

Worldwide, approximately how many rockets have been launched to date

oksian1 [2.3K]

Answer:

about 35,000-40,000

Explanation:

4 0

3 years ago