Semester: Sept 2015 – Jan 2015
Course: PHY440 Mechanics, Waves and Thermal Physics
Text book: Jewett, J.W. and Serway, R.A. (2010). Physics for Scientists and Engineers with Modern Physics, 8th Edition, Brooks/Cole Cengage Learning.
Assignment 4
Question / Topic / Problem1 / Section 14.2 Variation of Pressure with Depth / No 11 (Softcopy) p.424; No 9 (Hardcopy) p. 424
11. (a) Calculate the absolute pressure at the bottom of a freshwater lake at a point whose depth is 27.5 m. Assume the density of the water is 1.00 ´ 103 kg/m3 and that the air above is at a pressure of 101.3 kPa. (b) What force is exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diameter of 35.0 cm?
2 / Section 14.4 Buoyant Forces and Archimedes’s Principle / No 33 (Softcopy) p.426; No 31 (Hardcopy) p. 426
33. A large weather balloon whose mass is 226 kg is filled with helium gas until its volume is 325 m3. Assume the density of air is 1.20 kg/m3 and the density of helium is 0.179 kg/m3. (a) Calculate the buoyant force acting on the balloon. (b) Find the net force on the balloon and determine whether the balloon will rise or fall after it is released. (c) What additional mass can the balloon support
in equilibrium?
3 / Section 14.6 Bernoulli’s Equation / No 42 (Softcopy) p.427; No 40 (Hardcopy) p. 427
42. Water falls over a dam of height h with a mass flow rate of R, in units of kilograms per second. (a) Show that the power available from the water is
P = Rgh
where g is the free-fall acceleration. (b) Each hydroelectric unit at the Grand Coulee Dam takes in water at a rate of 8.50 x 105 kg/s from a height of 87.0 m. The power developed by the falling water is converted to electric power with an efficiency of 85.0%. How much electric power does each hydroelectric unit produce?
4 / Section 14.7 Other Applications of Fluid Dynamics / No 49 (Softcopy) p.428; No 49 (Hardcopy) p. 428
49. An airplane is cruising at altitude 10 km. The pressure outside the craft is 0.287 atm; within the passenger compartment, the pressure is 1.00 atm and the temperature is 20°C. A small leak occurs in one of the window seals in the passenger compartment. Model the air as an ideal fluid to estimate the speed of the airstream flowing through the leak.
5 / Section 16.2 Analysis Model: Traveling Wave / No 15 (Softcopy) p.483; No 17 (Hardcopy) p. 484
15. A transverse wave on a string is described by the wave
function
y = 0.120 sin π8x+4πt
where x and y are in meters and t is in seconds. Determine (a) the transverse speed and (b) the transverse acceleration at t = 0.200 s for an element of the string located at x = 1.60 m. What are (c) the wavelength, (d) the period, and (e) the speed of propagation of this wave?
6 / Section 16.3 The Speed of Waves on Strings / No 29 (Softcopy) p.484; No 29 (Hardcopy) p. 484
29. Tension is maintained in a string as in Figure P16.29. The observed wave speed is v = 24.0 m/s when the suspended mass is m = 3.00 kg. (a) What is the mass per unit length of the string? (b) What is the wave speed when the suspended mass is m = 2.00 kg?
7 / Section 19.4 Thermal Expansion of Solids and Liquids / No 9 (Softcopy) p.559; No 7 (Hardcopy) p. 559
9. The active element of a certain laser is made of a glass rod 30.0 cm long and 1.50 cm in diameter. Assume the average coefficient of linear expansion of the glass is equal to 9.00 ´ 10-6 (°C)-1. If the temperature of the rod increases by 65.0°C, what is the increase in (a) its length, (b) its diameter, and (c) its volume?
8 / Section 20.2 Specific Heat and Calorimetry / No 12 (Softcopy) p.593; No 8 (Hardcopy) p. 593
12. A 3.00-g copper coin at 25.0°C drops 50.0 m to the ground. (a) Assuming 60.0% of the change in gravitational potential energy of the coin–Earth system goes into increasing the internal energy of the coin, determine the coin’s final temperature. (b) What If? Does the result depend on the mass of the coin? Explain.
9 / Section 20.3 Latent Heat / No 16 (Softcopy) p.593; No 20 (Hardcopy) p. 594
16. A 3.00-g lead bullet at 30.0°C is fired at a speed of 240 m/s
into a large block of ice at 0°C, in which it becomes embedded.
What quantity of ice melts?
10 / Section 20.4 Work and Heat in Thermodynamic Processes / No 25 (Softcopy) p.594; No 25 (Hardcopy) p. 594
25. One mole of an ideal gas is warmed slowly so that it goes from the PV state (Pi , Vi ) to (3Pi, 3Vi ) in such a way that the pressure of the gas is directly proportional to the volume. (a) How much work is done on the gas in the process? (b) How is the temperature of the gas related to its volume during this process?
11 / Section 20.5 The First Law of Thermodynamics / No 26 (Softcopy) p.594; No 26 (Hardcopy) p. 594
26. A gas is taken through the cyclic process described in Figure P20.26. (a) Find the net energy transferred to the system by heat during one complete cycle. (b) What If? If the cycle is reversed—that is, the process follows the path ACBA—what is the net energy
input per cycle by heat?
12 / Section 20.6 Some Applications of the First Law
of Thermodynamics / No 31 (Softcopy) p.594; No 33 (Hardcopy) p. 595
31. An ideal gas initially at 300 K undergoes an isobaric expansion
at 2.50 kPa. If the volume increases from 1.00 m3 to3.00 m3 and 12.5 kJ is transferred to the gas by heat, what are (a) the change in its internal energy and (b) its final temperature?
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