HW3 spring 2011(1)

# HW3 spring 2011(1) - b. If it takes 6 hours to charge a...

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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) 2. It takes a force of 20 N to compress a spring a distance of 40 cm. What is the elastic potential energy of the spring at this position? Assume the spring obeys Hooke’s law. (5 pts) 3. A laptop uses a lithium-ion battery that can output 1500 milliamps at 5.7 volts. a. How much electrical work can the laptop battery produce (in watts)? (4 pts)
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Unformatted text preview: b. If it takes 6 hours to charge a completely dead laptop battery and energy costs \$0.13 per kilowatt-hour, what is the cost of recharging the battery a hundred times? (4 pts) 4. A gas is confined in a horizontal piston-cylinder device with a diameter of 0.47 m. Heat is applied to the piston-cylinder and causes the piston to expand by 0.83 meters. Assume atmospheric pressure is 101 kPa. a. How much work is done by the gas when it expands? (4 pts) b. How much heat was applied to the piston-cylinder? (3 pts) c. What is the speed of the piston just before it reaches equilibrium? The mass of the piston is 50 kg. (4 pts)...
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