Lake Mead, the reservoir above Hoover Dam, has a surface area of approximately 640 km2. The top 1 meter of water in the lake weighs about 6.3 x 1012 N. The dam holds that top layer of water 220 m above the river below, What is the potential energy of the top 1 m of water in Lake Mead. Group of answer choices

140800 j

2156 j

1.38 x 10^15 j

14367.3 j

Mike walks 100 meter north, then walks 30 meters south. after this, he walks another 10 meters north. what is the magnitude of his total displacement during this walk,in meters?

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!

Holes drilled several kilometers into earth’s crust provide direct evidence about earth’s interior in the form of