Hwk4B - 3 . 00 10-16 kg in air at 300 K. (b) Would the...

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PHYS 153 Homework 4B Problem 1 You blow up a spherical balloon to a diameter of 50 . 0 cm until the absolute pressure inside is 1 . 25 atm and the temperature is 22 . 0 C. Assume that in the balloon is the gas N 2 of molar mass 28 . 0 g / mol. (a) Find the mass of a single N 2 molecule. (b) How much translational kinetic energy does an average N 2 molecule have? (c) How many N 2 molecules are in the balloon? (d) What is the total translational kinetic energy of all the molecules in the balloon? Problem 2 Smoke particles in the air typically have masses of the order of 10 - 16 kg. The Brownian motion (rapid, irregular movement) of these particles, resulting from collisions with air molecules, can be observed with a microscope. (a) Find the root-mean-square speed of Brownian motion for a particle with a mass of
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Unformatted text preview: 3 . 00 10-16 kg in air at 300 K. (b) Would the root-mean-square speed be dierent if the particle were in hydrogen gas at the same temperature? Explain. Problem 3 One end of a solid cylindrical copper rod 0 . 200 m long is maintained at a temperature of 20 . 0 K. The other end is blackened and exposed to thermal radiation from surrounding walls at 500 . 0 K. The sides of the rod are insulated, so no energy is lost or gained except at the ends of the rod. When equilibrium is reached, what is the temperature of the blackened end? ( Hint: Since copper is a very good conductor of heat at low temperature, with k = 1670 W / m K at 20 K, the temperature of the blackened end is only slightly higher than 20 . 00 K.) 1 - 1...
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