30. (a) calculate the rate of heat conduction through house walls that are 13.0 cm thick and that have an average thermal conductivity twice that of glass wool. assume there are no windows or doors. the surface area of the walls is 120m2 and their inside surface is at 18.0ºc, while their outside surface is at 5.00ºc. (b) how many 1-kw room heaters would be needed to balance the heat transfer due to conduction?

(a) 960 W

(b) 960

Explanation:

d = 13 cm = 0.13 m

K = 2 times thermal conductivity of glass wool

K = 2 x 0.040 = 0.080 W/mK

A = 120 m^2

T1 = 18°C

T2 = 5°C

(a) The rate of conduction is given by

H = 960 W

(b)

Number of heaters = total power / power of one heater

Number of heaters = 960 / 1 = 960

explanation:

newton's third law, for every action there is an equal and opposite reaction.

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.