Need help with these physics questions. Ch. 11,13,14,15 1. A bicycle generator h

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Need help with these physics questions.

Ch. 11,13,14,15 1. A bicycle generator has a nider that cam provide 210 Wofpo 1. surroundings How much usable work s produced and what is the efficiency of the machine? A bicycle generator has a rider that can provide 210 W of power and 170W of heat is lost to the surroundings. How much usable work is produced 2. An engine runs at a high temperature of 375 with an ideal Carnot(ideal) efficiency of 31. What is the temperature of the exhaust? 3. A freezer uses 120 W of power to extract energy from the inside at a rate of 410 W. What is its coefficient of performance? 4. How much heat (in J) is required to evaporate 250g of water at 25'C 5. A change in entropy of 25 caVK occurs when ice melts at 0 "C, what is the mass of the ice? 6. What is the speed of a wave on a violin string that has a length of 59 cm and a fundamental frequency of 410 Hz? 7. A simple pendulum is formed when a spider hangs from a 12 cm length of web. What is the 8. A spring with a constant of 250 N/m has a 50g weight attached. What is the period of 9. A container has 35 mol of Neon at a pressure of 2 atm and a temperature of 25 "C. What is the 10. The air in a tire is at a pressure of 35 psi at a temperature of 21 'C. What is the new period of the motion? What is the frequency? oscillation? volume of the container? temperature if the pressure increases to 38 psi?

Explanation / Answer

Heat supplied Q = 210 W

Heat lost Q ' = 170 W

Usable Work W ' = Q - Q ' = 40 W

Efficiency = W ' / Q

               = 40 W / 210 W

               = 0.19

(2).High temprature T = 375 oC = 375 + 273 = 648 K

Efficiency n= 0.31

Cold temprature T ' = ?

We know n = 1-(T ' / T )

            0.31 = 1-(T ' / 648)

T ' / 648 = 1-0.31

               = 0.69

           T ' = 447.12 K

                = 447.12-273

                = 174.12 o C

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