What is the velocity of 10km west in three hours

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.

c. 4.54 x 10–12 j happens to be correct

it is the minimum amount of material needed to sustain a fission reaction.

critical mass is the minimum amount of fissionable material that must be assembled for a sustained fission reaction to take place. although two to three neutrons are produced for every fission, not all of these neutrons are available for continuing the fission reaction. if the conditions are such that the neutrons are lost at a faster rate than they are formed by fission, the chain reaction will not be self-sustaining.   at the point where the chain reaction can become self-sustaining, this is referred to as critical mass.