Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls are maintained at a temperature of 130°c. circular aluminum alloy 2024-t6 fins (k = 186 w/m⋅k) of outer diameter 6 cm and constant thickness 1 mm are attached to the tube. the space between the fins is 3 mm, and thus there are 250 fins per meter length of the tube. heat is transferred to the surrounding air at t[infinity] = 25°c, with a heat transfer coefficient of 40 w/m2⋅k. determine the increase in heat transfer from the tube per meter of its length as a result of adding fins.

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) .

In one or two sentences, describe how you did in the balancing game. in a few more sentences, explain one strategy you learned for balancing more complex equations.

What are the starting materials for nuclear fission? two small nuclei two large nuclei a neutron and a large nucleus a neutron and a small nucleus