Chemical reaction to make a foam?

Acylindrical specimen of a nickel alloy having an elastic modulus of 207 gpa (30 × 106psi) and an original diameter of 10.2 mm (0.40 in.) experiences only elastic deformation when a tensile load of 8900 n (2000 lbf) is applied. compute the maximum length of the specimen before deformation if the maximum allowable elongation is 0.25 mm (0.010 in.)

Two large, flat, horizontally oriented plates are parallel to each other, a distance d apart. half way betwween the two plates the electric field has magnitude e. if the separation of the plates is reduced to d/2 what is the magnitude of the electric field half way between the plates?

Need people build a dam to create a reservoir that supplies water a nearby city needs. describe two ways this action will likely affect the water cycle in the local environment. (5 points) worth 20 points