Imagine a copper wire 10 km long that needs to supply a city with 10 Mwatts of power--say from a waterfall. If the city ran on DC power, with voltages of 100 V, how much current would run through that wire? If you were willing to lose 1% of your power as heat in the wire, how thick would such a wire have to be? The resistivity of copper is 1.7 x 10-8 ohm-m.

Tafari worked one summer on a ship that set weather buoys in the ocean. he watched how one of the buoys moved in the water. describe which parts of the wave would cause the buoy to bob up and down. which wave property determined how fast the buoys bobbed in the water? he observed that when the wind blew harder, the ocean waves were larger, and the buoys moved away from the ship. what effect, if any, did the waves have on how far the buoys moved? explain your answer.

Sound is a disturbance that travels through a medium as a

An object with initial temperature 130 ∘ f is submerged in large tank of water whose temperature is 50 ∘ f . find a formula for f ( t ) , the temperature of the object after t minutes, if the cooling constant is k = − 0.2 . remember newton's law of cooling (the rate of change of temperature with respect to time is equal to k times the difference between the temperature of the object and the surrounding temperature) ! : )