7. A block rests on a frictionless table on Earth. After a 20-N horizontal force is applied to the
block, it accelerates at 3.9 m/s^2.Then the block and table are carried to the moon, where the
acceleration due to gravity is 1.62 m/s^2. A horizontal force of 10 N is then applied to the block.
What is the acceleration?
A)2.0 m/s2
B)2.1 m/s2
C)1.8 m/s2
D)2.3 m/s2
E)2.5 m/s2

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

Agas contained within a piston-cylinder assembly undergoes three processes in series: process 12: compression with pv= constant from 1 bar and 1 liter to 4 bar. process 23: constant pressure expansion to 1 liter. process 31: constant volume calculate the pressure and volume at each state, and sketch the processes on a p-vdiagram labeled with pressure and volume values at each numbered stat

Why does lightning travel from clouds to the ground?