Problems
Problems

 1 The average speed of the atoms in a gas is 3 km/s. If the temperature of the gas is tripled, what would be the average speed of the atoms? 2 Hydrogen atoms at 300 K have an average speed of 2.5 km/s. At what temperature would hydrogen atoms have an average speed of 1.0 km/s? 3 A gas contains a mixture of hydrogen atoms and neon atoms (which contain 10 protons and 10 neutrons). How does the average speed of the neon atoms compare with the average speed of the hydrogen atoms? 4 Suppose a satellite has an escape velocity of 1.5 km/s. Oxygen atoms in the exosphere of the satellite have a temperature of 300 K and an average speed of 0.6 km/s. To what temperature would the exosphere have to cool to become low enough that oxygen atoms couldn't escape? 5 What happens to the pressure of a gas if both its temperature and density double? 6 What would have to happen to the temperature of a gas in order for its density to double and its pressure to fall to 40% of its original value? 7 At what altitude in the Earth's atmosphere is the pressure equal to 1/32 of the pressure at sea level? 8 At a depth of 1 km in the ocean the pressure is 107 N/m2. What is the weight of the water that is in a cylinder 1 km high that has a cross-sectional area of 1 m2? 9 The atmospheric pressure at sea level is 105 N/m2. Estimate the surface area of your body and use that area to calculate the total force pushing inward on your skin. 10 A blackbody is brightest at a wavelength of 800 nm. At what wavelength would the blackbody be brightest if its temperature were tripled? 11 The wavelength at which blackbody A is brightest is four times the wavelength at which blackbody B is brightest. How does the temperature of blackbody A compare with the temperature of blackbody B? 12 A blackbody has a temperature of 5 K. At what wavelength is it brightest? 13 Suppose the temperature of a blackbody increases by 20%. What will happen to the total rate at which it radiates energy? 14 Two blackbodies have the same size. One of them radiates energy at 10 million times the rate of the other. How do the temperatures of the blackbodies compare? 15 How does the brightness of sunlight at Saturn's distance compare with the brightness at 1 AU? 16 Two satellites of the same planet have albedos of 0.8 and 0.3. Which of the satellites will have a higher surface temperature? (Assume that the satellites are identical except in albedo.) 17 Atoms of an unstable isotope are made in a nuclear physics laboratory. After 6 minutes only 1/4 of the original atoms are left. What is the half-life of the isotope? 18 The half-life of an unstable isotope is 10 years. After what length of time would there be less than 1% of the original atoms of the isotope remaining? 19 What fraction of the original 14C remains after 100,000 years?

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