A pendulum of mass 22 kg is released from rest at some height, as shown by point A in the image below. At the bottom of its arc at point B, it is traveling at
a speed of 13 m/s. What is the approximate amount of energy that has been
lost due to friction and air resistance? (Recall that g = 9.8 m/s2)

28. a stone is projected at a cliff of height h with an initial speed of 42.0 mls directed at angle θ0 = 60.0° above the horizontal. the stone strikes at a, 5.50 s after launching. find (a) the height h of the cliff, (b) the speed of the stone just before impact at a, and (c) the maximum height h reached above the grou

When a book falls from a shelf to the ground without anyone pushing on it, no work is done on the book. true or false

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