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Korolek [52]
3 years ago
12

An electric furnace is to melt 40 kg of aluminium/hour. The initial temperature of aluminium is 32°C. Given that aluminium has s

pecific heat capacity 950 J/kg K melting point 680*C, latent heat of fusion 450 kJ/kg, the efficiency of furnace is 85% and cost of energy is 20 cents/kWhr Calculate: (a) Power required (b) The cost of operating the furnace for 30 hours
Physics
1 answer:
gizmo_the_mogwai [7]3 years ago
3 0

Answer:

Part a)

P = 13.93 kW

Part b)

R = 8357.6 Cents

Explanation:

Part A)

heat required to melt the aluminium is given by

Q = ms\Delta T + mL

here we have

Q = 40(950)(680 - 32) + 40(450 \times 10^3)

Q = 24624 kJ + 18000 kJ

Q = 42624 kJ

Since this is the amount of aluminium per hour

so power required to melt is given by

P = \frac{Q}{t}

P = \frac{42624}{3600} kW

P = 11.84 kW

Since the efficiency is 85% so actual power required will be

P = \frac{11.84}{0.85} = 13.93 kW

Part B)

Total energy consumed by the furnace for 30 hours

Energy = power \times time

Energy = 13.93 kW\times 30 h

Energy = 417.9 kWh

now the total cost of energy consumption is given as

R = P \times 20 \frac{Cents}{kWh}

R = 417.9 kWh\times  20 \frac{cents}{kWh}

R = 8357.6 Cents

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horrorfan [7]

Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.

Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. .

Newton's third law: All forces in the universe occur in equal but oppositely directed pairs.

6 0
2 years ago
Suppose kinetic energy is 4 joules of a moving object what will happen if we increase the speed twice
Artyom0805 [142]

Answer:

The kinetic energy is 16 joules.                        

Explanation:

Kinetic energy (E) is given by:

E = \frac{1}{2}mv^{2}

Where:

m: is the mass

v: is the speed

When the kinetic energy is 4 joules, the speed of the object is:

v_{1}^{2} = \frac{2E_{1}}{m} = \frac{8}{m}                         

Now, if the speed is increased twice then we have:

E_{2} = \frac{1}{2}mv_{2}^{2} = \frac{1}{2}m(2v_{1})^{2} = \frac{1}{2}m[4(\frac{8}{m})] = 16 J

Therefore, the kinetic energy is 4 times the initial value.  

I hope it helps you!                                

3 0
2 years ago
A factory worker pushes a 32.0 kg crate a distance of 7.0 m along a level floor at constant velocity by pushing horizontally on
g100num [7]

Answer:

(a) 81.54 N

(b) 570.75 J

(c) - 570.75 J

(d) 0 J, 0 J

(e) 0 J  

Explanation:

mass of crate, m = 32 kg

distance, s = 7 m

coefficient of friction = 0.26

(a) As it is moving with constant velocity so the force applied is equal to the friction force.

F = 0.26 x m x g = 0.26 x 32 x 9.8 = 81.54 N

(b) The work done on the crate

W = F x s = 81.54 x 7 = 570.75 J

(c) Work done by the friction

W' = - W = - 570.75 J

(d) Work done by the normal force

W'' = m g cos 90 = 0 J

Work done by the gravity

Wg = m g cos 90 = 0 J

(e) The total work done is

Wnet = W + W' + W'' + Wg = 570.75 - 570.75 + 0 = 0 J  

6 0
3 years ago
An instructor gives a demonstration in which he makes a standing wave on a long thin slinky. The slinky is 6.0 meters long. If y
Naily [24]

The characteristics of standing waves allows to find the result for the speed of the wave is:

  • The speed wave is:  v = 10 m / s

The wave is a way of transmitting energy without mass displacement, , in the attachment we can see a diagram of the standing wave.

Each cycle corresponds to half a wavelength,  they indicate that the frequency is 2.50 Hz and there are three cycles, so the wavelength is:

      L = n \frac{\lambda}{2}

      λ = 2L/n

      λ = 2 6 /3

       λ = 4 m

Wave speed is related to wavelength and frequency

        v = λ f

         v = 4 2.5

         v = 10 m / s

In conclusion, using the characteristics of standing waves we can find the result for the speed of the wave is:

  • The wave speed is:   v = 10 m / s

Learn more here: brainly.com/question/12536719

8 0
3 years ago
What is the total resistance in the circuit? (include unit in answer - ohms)
solmaris [256]

Answer:60 ohms

Explanation:

R1=30 ohms

R2=15 ohms

R3=15 ohms

Let the total resistance be R

R=R1 + R2 + R3

R=30 + 15 +15

R=60

Total resistance is 60 ohms

4 0
3 years ago
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