In the bohr model of the hydrogen atom, an electron({rm mass}; m=9.1; times 10^{ - 31; }{rm kg}) orbits a proton at a distance of 5.3 times 10^{ - 11; }{rm m}. the proton pulls on the electron with an electricforce of 8.2 times 10^{ - 8}; {rm n}. how many revolutions per second does theelectron make?

Why do scientists believe that light is made of streams of particles? scientists believe that light is made of streams of particles because only the presence of photons can explain phenomena observed during experiments on the photoelectric effect. these observations include only some frequencies of light causing the ejection of electrons, no time gap existing between light striking a metal and electrons being ejected, and intensity having no effect on the kinetic energy of the ejected electrons.

A23 kg log of wood begins from rest, 300 m up a sluice (a water track used to transport logs, think of it as an inclined plane with negligible friction) inclined at 20° to the horizontal. after it reaches the flat waterway at the bottom it collides elastically with a 100 kg block of wood initially at rest near the base of the incline. (a) how long does it take the 23 kg log to travel down the incline? (b) what is the speed of the 23 kg log at the bottom of the incline? (c) what are the velocities of both blocks of wood after the collision? (d) what is the total kinetic energy before the collision? (e) what is the kinetic energy of the 23 kg log after the collision? (f) what is the kinetic energy of the 100 kg block of wood after the collision? (g) what is the total kinetic energy after the collision? (h) compare the total initial and total final kinetic energies. is this consistent with what you would expect for elastic collisions? explain!

22. the effect of threshold braking is to a cause skids. b. lock wheels. c. prevent locking of wheels. d. increase stopping distance.