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baherus [9]
3 years ago
15

A refrigerator is removing heat from a cold medium at 3∘C at a rate of 5400 kJ/h and rejecting the waste heat to a medium at 30∘

C. If the coefficient of performance of the refrigerator is 2, the power consumed by the refrigerator is
(a) 0.5 kW
(b) 0.75 kW
(c) 1.0 kW
(d) 1.5 kW
(e) 3.0 kW
Physics
1 answer:
ipn [44]3 years ago
3 0

Answer:(b) 0.75 kW

Explanation:

Given

temperature of cold region T_L=3^{\circ}C

Heat removal at the rate of Q_1=5400 kJ/h

temperature of hot region T_H=30^{\circ}C

COP of refrigerator =2

COP of a refrigerator is given by ratio of desired effect to the Power input

COP=\frac{Q_1}{Power}

2=\frac{5400}{P}

P=2700 kJ/h

P=0.75 kW

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a line passes through (8,-4) and has a slope 2/3. what is an equation in point slope form of the line? An equation of the line i
evablogger [386]

from the question

x₁ = x-coordinate = 8

y₁ = y-coordinate = - 4

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slope form of the line is given as

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inserting the values

(y - (- 4) ) = (2/3) (x - 8)

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7 0
3 years ago
A train leaves the train station at noon and travels at a constant speed of vt = 50 mi/hr on a straight track. 2 hr later, a car
asambeis [7]

Answer:

350 miles

Explanation:

When the car starts 2 hours later, the train would have a head start of

50 * 2 = 100 miles

The speed of the car relative to the train is

70 - 50 = 20 mi/hr

For the car to catch up with the train, it must cover the 100 miles difference at the rate of 20mi/hr. So the time it would need to cover this difference is

100 / 20 = 5 hours

After 5 hours, the car would have traveled a distance of

5 * 70 = 350 miles which is also the distance from the station to where the car catches up

6 0
3 years ago
a street light is mounted at the top of a 15 foot pole. A man 6 ft tall walks away from the pole wit a speed of 7 ft/s along a s
Mariulka [41]

Answer:

16.3 ft/s

Explanation:

Let d=distance

and

x = length of shadow.

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x=(d + x)

 = 6/15

So,

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     9x = 6d.

x = (2/3)d.

As we know that:

dx=dt

   = (2/3) (d/dt) 

Also,

Given:

d(d)=dt

     = 7 ft/s

Thus,

d(d + x)=dt

           = (7/3)d (d/dt)

Substitute, d= 7  

d(d + x) = 49/3 ft/s.

Hence,

d(d + x) = 16.3 ft/s.

4 0
3 years ago
What’s an example of contact friction
kotegsom [21]

Answer:

a nightstand on a lamp table

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