The 150-mm-thick wall of a gas-fired furnace is constructed of fireclay brick (k = 1.5 w/m k, = 2600 kg/m3, cp = 1000 j/kg k) and is well insulated at its outer surface. the wall is at a uniform initial temperature of 20°c, when the burners are fired and the inner surface is exposed to products of combustion for which t[infinity] = 950°c and h = 100 w/m2 k. (a) how long does it take for the outer surface of the wall to reach a temperature of 750°c? (b) plot the temperature distribution in the wall at the foregoing time, as well as at several intermediate times.

Apositive point charge q is fixed on a very large horizontal frictionless tabletop. a second positive point charge q is released from rest near the stationary charge and is free to move. which statement best describes the motion of q after it is released? assume q stays on the table

In a thunderstorm, charge builds up on the water droplets or ice crystals in a cloud. thus, the charge can be considered to be distributed uniformly throughout the cloud. for the purposes of this problem, take the cloud to be a sphere of diameter 1.00 kilometer. the point of this problem is to estimate the maximum amount of charge that this cloud can contain, assuming that the charge builds up until the electric field at the surface of the cloud reaches the value at which the surrounding air breaks down. this breakdown means that the air becomes highly ionized, enabling it to conduct the charge from the cloud to the ground or another nearby cloud. the ionized air will then emit light due to the recombination of the electrons and atoms to form excited molecules that radiate light. in addition, the large current will heat up the air, resulting in its rapid expansion. these two phenomena account for the appearance of lightning and the sound of thunder. take the breakdown electric field of air to be eb=3.00ă—106n/c. part a estimate the total charge q on the cloud when the breakdown of the surrounding air is reached. express your answer numerically, to three significant figures, using ďµ0=8.85ă—10â’12c2/(nâ‹…m2) .

Ineed the answer to question 1 , i’m desperate