From the 1930s to the 1970s, extensive groundwater pumping in the San Joaquin Valley of California caused the ground to subside by as much as 9 m. How does groundwater withdrawal contribute to land subsidence?
What will be an ideal response?
Answer: Land subsidence can occur in areas underlain by thick sequences of poorly consolidated sediments. As water is pumped from an aquifer with layers of easily compressed water—bearing clays (low-permeability) interbedded with layers of sandy (high-permeability) rock, water slowly leaks out of the clay layers. As the clays become dewatered, they compact, and the land subsides.
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When an apple that weighs 1 N is dropped and freely falls, the net force on the apple is
A) 0 N. B) 0.1 N. C) 1 N. D) 10 N. E) none of the above
A 2.0-kg block slides down a fixed, rough curved track. The block has a speed of 5.0 m/s after its height above a horizontal surface has decreased by 1.8 m. Assume the block starts from rest. What is the change in mechanical energy of the block caused by the force of friction during this descent?
a. ?14 J b. ?12 J c. ?10 J d. ?16 J e. ?25 J
If both mass and velocity of a ball are doubled, the kinetic energy is increased by a factor of:
a. 16. c. 4. b. 8. d. 2.
Three point charges are placed on the x-axis. A charge of +2.0 ?C is placed at the origin, -2.0 ?C to the right at x = 50 cm, and +4.0 ?C at the 100 cm mark
What are the magnitude and direction of the electrostatic force that acts on the charge at the origin? (k = 1/4??0 = 8.99 × 109 N ? m2/C2)