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frutty [35]
2 years ago
7

A power plant burns 1000 kg of coal each hour and produces 500 kW of power. Calculate the overall thermal efficiency if each kg

of coal produces 6 MJ of energy.
Physics
1 answer:
solniwko [45]2 years ago
5 0

Answer:

The overall thermal efficiency is 30%.

Explanation:

Given;

Output power = 500 kWh

input energy  per kg of coal = 6 MJ = 6 x 10⁶ J = 1.66667 kWh

1000 kg of coal will produce 1000 x 1.66667 kWh = 1666.67 kWh

Thus, total input power = 1666.67 kWh

Overall thermal efficiency = Total output power/Total input Power

Overall thermal efficiency = (500/1666.67) *100

Overall thermal efficiency = 0.29999 *100

Overall thermal efficiency = 30%

Therefore, the overall thermal efficiency is 30%.

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A speaker fixed to a moving platform moves toward a wall, emitting a steady sound with a frequency of 245 Hz. A person on the pl
Luba_88 [7]

Answer:

Explanation:

by Doppler effect

F apparent = F real x (Vair +- Vobserver) / (Vair +- Vsource)

case1 :if observer is approaching a source then put a + in numerator and - in denominator

case 2 : if observer is going away from source then do opposite.

it is case1 cos observer is moving toward wall . actually wall is acting as a source for observer

so

F apparent = 240 x (344 + vp ) / (344 - vp )

now F apparent - Freal = beat frequency of 6.00 Hz

so {240 x (344 + vp ) / (344 - vp )} - 230 = 6

240 x (344 + vp -344 + vp) / (344 - vp ) = 6

240 x 2 x vp = 6 x (344 - vp )

480 vp = 2064 - 6 x vp

486 x vp = 2064

vp = 4.24 m/s

4 0
2 years ago
A 2.0-kg box and a 3.0-kg box on a perfectly smooth horizontal floor have a spring of force constant 250 N/m compressed between
svp [43]

Answer:

7.5 m/s² and 5 m/s²

Explanation:

Note: The force in the compressed spring is the same as the force needed to produce the acceleration in each box.

From Hook's law,

F = ke..................... Equation 1

Where F = force, k = spring constant, e = compression.

Given: k = 250 N/m, e = 6.0 cm = 0.06 m

Substitute into equation 1

F = 250×0.06

F = 15 N.

Using Newton's fundamental equation of kinematics

F = ma.................. Equation 2

Where m = mass of the box, a = acceleration of the box.

make a the subject of the equation

a = F/m................. Equation 3

For the first box,

Given: m = 2.0 kg, F = 15 N

Substitute into equation 3

a = 15/2.0

a = 7.5 m/s².

For the second box,

Give: m = 3.0 kg, F = 15 N

Substitute into equation 3

a = 15/3

a = 5 m/s²

8 0
2 years ago
Read 2 more answers
Which of the following describes the time over which a periodic wave repeats?
sineoko [7]

Answer:

b

Explanation:

4 0
2 years ago
Which are characteristics of a ray when it hits a boundary and refracts, but not when it hits the boundary and reflects? Check a
mrs_skeptik [129]

Answer:

B. changes speed  

F. passes through the boundary

Explanation:

Only these two options are characteristics of a ray when it is refracted, but not when it is reflected. In fact:

Reflection occurs when a ray hits the interface between two mediums and bounces off back. When it is reflected, the ray changes direction, but does not change speed since it does not change medium.

Refraction occurs when a ray passes through the interface between two different mediums. When it is refracted, the ray changes direction, and it changes speed as well, since it changes medium.

Based on these definitions, we can say that only B. (changes speed) and F. (passes through the boundary) are properties of a refracted ray but NOT of a reflected ray. All the other choices are wrong because:

A. changes direction --> it is true for both reflection and refraction

C. does not change direction --> it is false

D. does not change speed --> it is false

E. bounces off the boundary --> it is true only for reflection

6 0
2 years ago
Read 2 more answers
A scientist is examining an unknown solid. Which procedure would most likely help determine a chemical property of the substance
kifflom [539]

Answer:

b. exposing it to a flame to see if it catches on fire

Explanation:

The Procedure will most likely help to determine a chemical property of  substance is : exposing material to a flame to see if it catches on fire Chemical property is the characteristic that a substance has that differentiate it from another substance. The most common charatcteristics that most scientists wanted to know are : - It's flammability - It's radioactivity - Its toxicity By throwing the object into fire, we will easily find out these 3 characteristics

Hence the correct answer is b. exposing it to a flame to see if it catches on fire.

3 0
2 years ago
Read 2 more answers
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