HW3 spring 2011 solutions

HW3 spring 2011 solutions - CHEG 2313 Thermo I HW#3 Spring...

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Unformatted text preview: CHEG 2313 Thermo I HW#3 Spring 2011 Due Wednesday, February 9, 2011 in class. 1. In snowy weather, the driver of a car going 30 mph slides down a 200 ft hill and then up a 225 ft. hill. Assuming that the driver never puts his foot on the gas or brake pedals, what will be the speed of the car once it is over the second hill? (6 pts)- System: car- start with energy balance - integrated W Q dt gh H M gh M U gh M U k K k t t k t t + + + + = + +- + + = 1 2 . . 2 2 2 2 2 2 1 1 2 - closed system so no mass flows- no heat or work- assume no internal energy changes no significant change in temperature or volume- reduced energy balance 2 2 1 2 2 2 = +- + t t gh M gh M - know: s ft hr mi / 44 / 30 1 = = m h m h 225 200 2 1 = =- substitute into equations and solve for final velocity ( 29 ( 29 mph s ft s ft ft s ft s ft gh gh gh M gh M 3 . 12 ~ 1 . 18 225 2 . 32 200 2 . 32 2 44 2 2 2 2 2 2 2 2 2 1 2 1 2 1 2 1 2 2 2 =...
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HW3 spring 2011 solutions - CHEG 2313 Thermo I HW#3 Spring...

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