Concept explainers
GO In a certain experiment, a small radioactive source must move at selected, extremely slow speeds. This motion is accomplished by fastening the source to one end of an aluminum rod and heating the central section of the rod in a controlled way. If the effective heated section of the rod in Fig. 18-31 has length d = 2.00 cm, at what constant rate must the temperature of the rod be changed if the source is to move at a constant speed of 100 nm/s?
Figure 18-31 Problem 20.
Trending nowThis is a popular solution!
Chapter 18 Solutions
Fundamentals of Physics, Volume 1, Chapter 1-20
Additional Science Textbook Solutions
Conceptual Integrated Science
Glencoe Physics: Principles and Problems, Student Edition
College Physics: A Strategic Approach (3rd Edition)
Physics for Scientists and Engineers
Introduction to Electrodynamics
- Even when shut down after a period of normal use, a large commercial nuclear reactor transfers thermal energy at the rate of 150 MW by the radioactive decay of fission products. This heat transfer causes a rapid increase in temperature if the cooling system fails (1 watt = 1 joule/second or 1 W = 1 J/s and 1 MW = 1 megawatt). (a) Calculate the rate of temperature increase in degrees Celsius per second (C/s) if the mass of the is 1.60105 kg and it has an average specific heat of 0.3349 kJ/kg . C. (b) How long would it take to obtain a temperature increase of 2000 C, which could cause some metals holding the radioactive materials to melt? (The initial rate of temperature increase would be greater than that calculated here because the heat transfer is concentrated in a smaller mass. Later, however, the temperature increase would slow down because the 500,000-kg steel containment vessel would also begin to heat up.)arrow_forwardAn aluminum rod 0.500 m in length and with a cross sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 3(H) K. (a) If one-halt of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool, (b) If the circular surface of the upper end of the rod is maintained at 300 K. what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 YV/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)arrow_forwardAn aluminum rod 0.500 m in length and with a cross-sectional area of 2.50 cm2 is inserted into a thermally insulated vessel containing liquid helium at 4.20 K. The rod is initially at 300 K. (a) If one-half of the rod is inserted into the helium, how many liters of helium boil off by the time the inserted half cools to 4.20 K? Assume the upper half does not yet cool. (b) If the circular surface of the upper end of the rod is maintained at 300 K, what is the approximate boil-off rate of liquid helium in liters per second after the lower half has reached 4.20 K? (Aluminum has thermal conductivity of 3 100 W/m K at 4.20 K; ignore its temperature variation. The density of liquid helium is 125 kg/m3.)arrow_forward
- A spherical vessel, with 30.0-cm outside diameter, is used as a reactor for a slow endothermic reaction. The vessel is completely submerged in a large water-filled tank, held at a constant temperature of 30°C. The outside surface temperature of the vessel is 20°C. Calculate the rate of heat transfer in steady operation for the following cases: (a) the water in the tank is still, (b) the water in the tank is still (as in a part a), however, the buoyancy force caused by the difference in water density is assumed to be negligible, and (c) the water in the tank is circulated at an average velocity of 20 cm/s.arrow_forwardThermography is a technique for measuring radiant heat and detecting variations in surface temperatures that may be medically, environmentally, or militarily meaningful.(a) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 33.0C, such as on a person’s skin? (b) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 20.0C, such as for warm and cool automobile hoods?arrow_forwardA tube of 50 mm diameter is heated electrically and receives a constant heat flux of 800 W/m. Water flows through the tube entering it at 25°C and the Reynolds number is 1600. Determine (a) the average heat transfer coefficient between the water and the tube wall, assuming fully developed conditions, (b) the length of the tube required for the bulk temperature of water to rise from 25°C to 50°C. For water at 25°C, take μ = 915 x 106 kg/m.s, k = 610 x 10-³. 9.00 Warrow_forward
- Ex 51: The temperature of interstellar space has an average value of about 5 K. Find the rms speed of a proton in the space. [mp = 1.673 x 10 27 kg, kB = 1.38 x 10 23 J/K]arrow_forwardA hot object is dropped into a thermally insulated container of water, and the object and water are then allowed to come to thermal equilibrium. The experiment is repeated twice, with different hot objects. All three objects have the same mass and initial temperature, and the mass and initial temperature of the water are the same in the three experiments. For each of the experiments, Fig. 18-29 gives graphs of the temperatures T of the object and the water versus time t. Rank the graphs according to the specific heats of the objects, greatest first.arrow_forwardA thermocouple, with a spherical junction diameter of 0.5 mm, is used for measuring the temperature of hot air flow in a circular duct. The convection heat transfer coefficient of the air flow can be related with the diameter (D) of the spherical junction and the average air flow velocity (V) as h = 2.2(V/D)0.5, where D, h, and V are in m, W/m2?K and m/s, respectively. The properties of the thermocouple junction are k = 35 W/m?K, r = 8500 kg/m3, and cp = 320 J/kg?K. Determine the minimum air flow velocity that the thermocouple can be used, if the maximum response time of the thermocouple to register 99 percent of the initial temperature difference is 5 s.arrow_forward
- A large heat exchanger transfers a total of 100 MW. Assume the wall separating steam and seawater is 4 mm of steel, conductivity 15 W/m K and that a maximum of 5°C difference between the two fluids is allowed. Find the required minimum area for the heat transfer.arrow_forwardThe average rate at which energy is conducted outward through the ground surface in North America is 54.0 mW/m2, and the average thermal conductivity of the near-surface rocks is 2.50 W/mK. Assuming a surface temperature of 10.0 C, find the temperature at a depth of 35.0 km (near the base of the crust). Ignore the heat generated by the presence of radioactive elements.arrow_forwardA) Estimate the total solar heating absorbed by the Earth every second. Assume 36% of the incoming solar radiation is reflected by clouds and lost. You can assume that the Earth intercepts sunlight with an effective area of πr2 where r is Earth’s radius. B) Estimate the total heat lost by the Earth as infrared radiation every second. Assume Earth has an effective temperature of 252 K (-21 C).arrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning