According to the laws of thermal radiation, hotter objects emit photons with .
a) a lower average frequency
b) a shorter average wavelength
c) a higher average speed
d) a lower average energy

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!

Most of the volume of an atom is occupied by the

The text compares alternating current with direct current. how are they different? a alternating current reverses direction in the electrical wiring. direct current flows in one direction only. b direct current reverses direction in the electrical wiring. alternating current flows in one direction only. c direct current is powered by solar energy. alternating current is powered by electrical energy. d alternating current does not move in the electrical wiring. direct current does move in the electrical wiring.