Asingle mass (m1 = 4.4 kg) hangs from a spring in a motionless elevator. the spring constant is k = 275 n/m.
now, three masses (m1 = 4.4 kg, m2 = 13.2 kg and m3 = 8.8) hang from three identical springs in a motionless elevator. the springs all have the same spring constant given above.
finally, the elevator is moving downward with a velocity of v = -2.1 m/s but accelerating downward at an acceleration of a = -2.1 m/s2.
what is the magnitude of the net force on the middle mass?

15. one purpose of the tread pattern on a tire is to a reduce tire wear. b. reduce traction c. allow water to flow away from the tire. d. look impressive.

Because air contracts as it cools, the air pressure inside a freezer is typically lower than on the outside. why do ice cubes inside a freezer tend to shrink over time? a. the ice dissolves oxygen from the air, forming a denser crystalline matrix.b. the ice reacts chemically with carbon dioxide in the air, forming gaseous carbon compounds.c. the ice melts, and then the liquid freezes as ice crystals on the bottom of the freezer.d. the ice sublimes, and then the water vapor deposits as ice crystals on the sides of the freezer.

Engines for propeller-driven aircraft are limited in their maximum rotational speed by the fact that the tip speed of the propeller must not approach the speed of sound in air (mach i). taking 6 ft as a typical diameter for a propeller of a light airplane and 1100 fils as the speed of sound, find the upper limit on the rpm (revolutions per minute) of the propeller shaft.