22. Which of the following statements best explains why it is usually easier to keep a sliding object moving than it is to start the object moving? A. Kinetic friction is typically equal to static friction. B. Kinetic friction is typically less than static friction. C. Kinetic friction is a force that resists attempts to start an object moving. D. Kinetic friction is a force that opposes the sliding of two objects over each other.

Which type of electromagnetic waves are dangerous enough to be used to kill cancerous cells? (a)gamma rays (b)visible light (c)infrared light (d)microwaves

Which simple machine is not part of this compound machine? a. lever b. pulley c. inclined plane d. wheel and axle

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