A 4500-kg helicopter accelerates upward at 2.0m/s? what lift force is exerted by the air on the helicopter?

Which is not a characteristic of a heat pump? a. it is used in air conditioners. b. it uses a refrigerant. c. it requires no work. d. it reverses the normal flow of thermal energy.

Apebble is thrown into a calm lake, ripples are formed from the center and move outward. the water particles in the lake travel in a circular pattern that moves up and down on the surface of a lake, and the energy travels a) diagonally. b) downward. c) horizontally. d) upward.

Looking at this barometer, is the air pressure high or low? what type of weather would you expect? high, bad low, bad high, good low, good