On ella's fifth birthday, her parents told her she had to stop whining or no one would want to play with her. she tried very hard to not whine. after a while, she decided that she didn't have anything to whine about. this is an example of: a. a token economy. b. learned optimism. c. learned . d. subjective being.

Athin, square metal plate measures 14 cm on each side and has emissivity of 0.60. the plate is heated to a temperature of 745°c. what is the rate at which the plate radiates energy ? the stefan-boltzmann constant is 5.67 × 10-8 w/(m2 ? k4). remember that the plate will radiate energy from both its top and bottom surfaces.

Acave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. the lift is performed in three stages, each requiring a vertical distance of 10.0 m: (a) the initially stationary spelunker is accelerated to a speed of 4.90 m/s; (b) he is then lifted at the constant speed of 4.90 m/s; (c) finally he is decelerated to zero speed. how much work is done on the 68.0 kg rescue by the force lifting him during each stage?

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?