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alukav5142 [94]
2 years ago
15

The cost of electricity varies widely throughout the United States; $0.120/kWh is a typical value. At this unit price, calculate

the cost of the following.
a. Leaving a 40.0-W porch light on for 2 weeks while you are on vacation.
b.Making a piece of dark toast in 3.00 min with a 980 W toaster.
c. Drying a load of clothes in 40.0 min in a 4900 W dryer.
Physics
1 answer:
strojnjashka [21]2 years ago
4 0

Answer: a) $1.6123 , b) $0.00588 c) $0.392

Explanation:

Note, all power in watts is converted to kilowatts and all units of time is converted to hours.

The cost of electricity is $0.12 for 1kwh.

Question a.

Power = 40w to kilowatts = 40/1000 = 0.04kw

Time = 2 weeks to hours = 24 * 14 = 336 h.

Energy = power * time.

Energy = 0.04 * 336 = 13.44kwh.

If 1kwh cost $0.12, then 13.44 kwh will cost

0.12 * 13.44 = $1.6132.

Question b

Power = 980w to kilowatts = 980/1000= 0.98kw

Time = 3 minutes to hours = 3/60 = 0.05 h

Energy = power * time

Energy = 0.98 * 0.05

Energy = 0.049kwh

If 1kwh cost $0.12, then 0.049 kwh will cost

0.049 * 0.12 = $0.00588

Question c

Power = 4900w to kilowatts = 4900/1000= 4.9kw.

Time = 40 minutes to hours = 40/ 60 = 0.67.

Energy = power * time

Energy = 4.9 * 0.67

Energy = 3.267 kwh

If 1 kwh cost $0.12, then 3.267kwh will cost

3.268 * 0.12 = $ 0.392

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3 years ago
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the idling engines of a landing turbojet produce forward thrust when operating in a normal manner, but they can produce reverse
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Forward thrust has positive values and reverse thrust has negative values.

Thrust is a sudden push or pull in a certain direction.

a)

Flight speed u = 150 km/h

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therefore, 150 km/h =  41.67 km / s

The thrust force represents the horizontal or x-component of momentum equation:

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b)

Now the exhaust velocity is now vertical due to reverse thrust application, then it has a zero horizontal component,

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The given question is incomplete, the complete question is,

"The idling engines of a landing turbojet produce forward thrust when operating in a normal manner, but they can produce reverse thrust if the jet is properly deflected. Suppose that while the aircraft rolls down the runway at 150 km/h the idling engine consumes air at 50 kg/s and produces an exhaust velocity of 150 m/s.

a. What is the forward thrust of this engine?

b. What are the magnitude and direction (i.e., forward or reverse) if the exhaust is deflected 90 degree without affecting the mass flow?

c. What are the magnitude and direction of the thrust (forward or reverse) after the plane has come to a stop, with 90 degree exhaust deflection and an airflow of 40 kg/s?"

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brainly.com/question/14552836

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