Attempt this weeks four (4) #MCAT questions to win a free month of Firecracker! Answers MUST include you reasoning and be submitted before we reveal correct answers the following mornings. Passage for Question 2: One of the major problems with energy production is figuring out how to store energy so more is available during high demand times and less is wasted during low demand times. There are many different types of energy storage, but so far the only method that has been effective on a large scale is pumped-storage hydroelectricity. Energy during cheap, lower demand times, such as nighttime, is used to pump water up to higher elevations so it is available at higher demand times. The energy stored in the reservoir is proportional to the height of the water in the reservoir. This is because although the water on the bottom of the reservoir has less gravitational potential energy than the water on the top, it is pressurized by the water above it, which gives it potential energy equal to the gravitational potential energy of the water above it. Thus the stored energy is equivalent to the potential energy if the entire mass of water was located at the height of the water on the top. Consider a reservoir used to produce hydroelectric power that uses the pump-storage method. The height of the water is 100m, and the reservoir can be modeled as a rectangular prism with sides of 2000m and 6000m. Take the density of water to be 1000kg/m^3 and atmospheric pressure to be 1.013*10^5 Pa. Question 2) Consider a 2m diameter pipe that comes out of the bottom of the reservoir. The pipe has a nozzle fixed to its end so that the diameter decreases to 1m. The nozzle is exposed to air, so it is at atmospheric pressure. What is the velocity of the water in the pipe before the nozzle? A) 177m/s B) 44m/s C) 7.8m/s D) 11m/s firecracker.me
Posted on: Tue, 05 Aug 2014 17:40:27 +0000
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