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Ipatiy [6.2K]
3 years ago
15

Number 29 plz help physics

Physics
1 answer:
svetoff [14.1K]3 years ago
8 0

Answer:

a. E = 900000 J = 900 KJ

b. ΔT = 8.18 °C

c. Cost = $ 7.2  

Explanation:

a.

The energy can be given by:

E = Pt

where,

E = Energy = ?

P = Power = 500 W

t = time = (0.5 h)(3600 s/1 h) = 1800 s

Therefore,

E = (500\ W)(1800\ s)

<u>E = 900000 J = 900 KJ</u>

b.

The change in temperature of room air is given by the following formula:

0.5E = mC\Delta T\\   (since 50% of energy is used to heat air)

where,

m = mass of air = 50 kg

C = specific heat of air = 1.1 KJ/kg.°C

ΔT = Change in temperature of air = ?

Therefore,

(0.5)(900\ KJ) = (50\ kg)(1.1\ KJ/Kg.^oC)\Delta T

<u>ΔT = 8.18 °C</u>

c.

First, we will calculate the total energy consumed:

E = (0.5\ KW)(6\ h/d)(30\ d)\\E = 90\ KWh

Now, for the cost:

Cost = (Unit\ Cost)(Energy)\\Cost = (\$ 0.08\KWh)(90\ KWh)

<u>Cost = $ 7.2</u>

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