Aballoon used in surgical procedures is cylindrical in shape. as it expands outward, assume that the length remains a constant . find the rate of change of surface area with respect to radius when the radius is (answer can be left in terms of π).

Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. this works through a process known as multiphoton absorption. in this process, several photons are absorbed at the same time. if very intense light whose photons carry 2ev of energy is shined onto a material with a band gap of 4ev, that light can be absorbed through two-photon absorption, because two photons have the right amount of energy to bridge the band gap. what is the minimum number of photons of 800-nm light that are needed to equal or exceed the band gap of fused silica glass

How much energy must a refrigerator absorb from 225 g of water so that the temperature of the water will drop from 35°c to 5°c

Debris produced by mining is called