Ametal bar is used to conduct heat. when the temperature at one end is 100°c and at the other is 20°c, heat is transferred at a rate of 16 j/s.

if the temperature of the hotter end is reduced to 80°c, what will be the rate of heat transfer?
a. 4 j/sb. 8 j/sc. 9 j/sd. 12 j/s

a. 4 J/s

Explanation:

Fourier's law states for the case in which there is stationary heat flow in only one direction, that is, linearly, the heat transmitted per unit of time is proportional to the temperature difference:

When the temperature at one end is 100°C and at the other is 20°C, we have:

If the temperature of the hotter end is , we have:

So:

Finally, we calculate the rate of heat transfer:

total distance travelled = 60 miles

total time taken =1.5 hours

average speed = total distance / total time

60 / 1.5

= 40

therefore, average speed = 40 m/h

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answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.