During a process, 30 J of work are done by a closed stationary system on its surroundings. The internal energy of the system decreases by 40 J. What is the heat transfer? Select the correct response: 70 J released into the surroundings 10 J absorbed by the system 10 J released into the surroundings 70 J absorbed by the system

During a process, 30 J of work are done by a closed stationary system on its surroundings. The internal energy of the system decreases by 40 J. What is the heat transfer? Select the correct response: 70 J released into the surroundings 10 J absorbed by the system 10 J released into the surroundings 70 J absorbed by the system

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.5P: To determine the thermal conductivity of a structural material, a large 15-cm-thick slab of the...

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To determine the thermal conductivity of a structural material, a large 15-cm-thick slab of the material is subjected to a uniform heat flux of 2500 W/m2 while thermocouples embedded in the wall at 2.5 cm. intervals are read over a period of time. After the system had reached equilibrium, an operator recorded the thermocouple readings shown below for two different environmental conditions: Distance from the Surface (cm) Temperature (C) Test 1 0 40 5 65 10 97 15 132 Test 2 0 95 5 130 10 168 15 208 From these data, determine an approximate expression for the thermal conductivity as a function of temperature between 40 and 208C.
A plane wall 15 cm thick has a thermal conductivity given by the relation k=2.0+0.0005T[W/mK] where T is in kelvin. If one surface of this wall is maintained at 150C and the other at 50C, determine the rate of heat transfer per square meter. Sketch the temperature distribution through the wall.
Air in a cylinder-piston system expands and works on the piston. The temperature of the air decreases during the process from the initial temperature of (30×1.6)°C down to the final temperature of 20°C. Specific heat values of air at constant pressure and constant volume are 1,000 J/kg.K and 730 J/kg.K respectively. (a) Determine the change of enthalpy per mass and the change of internal energy per mass, respectively. (b) This process produces 20 kJ/kg of work. Combine this number with your outcome from (a), to estimate the amount of heat transfer per mass required for this process to happen.c) Based on the outcome from part (b), determine whether the heat went ‘into’ the system or ‘out of’ the system.
Two very small metal point-like spheres with masses 5 g and 9 g are tied together by a 8 cm long massless string and are at rest on a frictionless surface. Each is charged to 11 uC. i.What is the energy (in J)of this system? a)13.6 b)20.4 c)44.4 d)11.8 e)5.31 f)28.7 ii.What is the tension (in N) in the string? a)555 b)359 c)170. d)66.4 e)148 f)255 iii.The string is cut. What is the speed (in m/s) of each sphere when they are far apart? (HINT: You will need to use TWO conservation laws here. One of them is Energy Conservation). Speed of m1a)23.1 b)125 c)59.2 d)88.7 e)193 f)51.5 Speed of m2a)69.4 b)107 c)32.9 d)12.8 e)28.6 f)49.3 Please answer all the parts neatly,correctly and completely and please show all the steps. Thankyou!
A 227 kg bear* is 15 ft up a tree when it falls onto a trampoline deforming it 3 ft (where it touches the ground). Neglecting friction and mass of the trampoline (and assuming the trampoline is a simple spring), what is the spring constant of the trampoline? 1 m = 3.3 ft * the bear was OK a. 24,470.60 N/m b. 2,441.93 N/m c. 741.53 N/m d. 7,415.33 N/m
Consider a college student who works from 7 P.M. to 11 P.M. assembling mechanical components. The number N of components assembled after t hours is given by the function below. At what time is the student assembling components at the greatest rate? N = 17t2 4 + t2 , 0 ≤ t ≤ 4 STEP 1: Begin by finding the first derivative of N. N'(t) = 136t(t2+4)2 STEP 2: Find the second derivative of N. N''(t) = −136(3t2−4)(t2+4)3 STEP 3: Solve for t by setting the second derivative of N equal to zero. t = 2√3 STEP 4: Find the third derivative of N. N'''(t) = 1632t(t+2)(t−2)(t2+4)4 STEP 5: Substitute the value for t from Step (3) into the equation for the third derivative of N. (Round your answer to two decimal places.) N''' = STEP 6: State the sign of N'''(t). N'''(t) ? < > 0 STEP 7: Select the most appropriate response. The student is assembling components at the greatest rate when t = 2√3…
40. Water flows through a pipe of varying cross-section and varying elevation at the rate of 22.2m3/min. At one section of the pipe 3 m from the ground, the radius of the pipe is 36 cm and the pressure is 12 N/cm^2.What is the pressure at a section where the radius of the pipe is 18cm and is 0.7 m from the ground level?A. 136 123 N/m2 B. 50 N/cm2 C. 750 000 N/m2 D. 12 N/cm2
Given the following situations, tell whether it applies the first law of thermodynamics or second law of thermodynamics. Draw a smiley face if applies the first law and a heart if it applies the second law. 1. Food digestion 2. Rusting of iron 3. Photosynthesis 4. Using aircon during summer 5. Simple motor 6. Growing younger 7. Plugging TV to watch a program 8. Riding a bicycle 9. Generator 10. Heat flows from lower to higher temperature
A metallic container of fixed volume of 2.5 × 10−3 m3 immersed in a large tank of temperature 27 °C contains two compartments separated by a freely movable wall. Initially, the wall is kept in place by a stopper so that there are 0.02 mol of the nitrogen gas on one side and 0.03 mol of the oxygen gas on the other side, each occupying half the volume. When the stopper is removed, the wall moves and comes to a final position. The movement of the wall is controlled so that the wall moves in infinitesimal quasi-static steps. (a) Find the final volumes of the two sides assuming the ideal gas behavior for the two gases. (b) How much work does each gas do on the other? (c) What is the change in the internal energy of each gas? (d) Find the amount of heat that enters or leaves each gas.
A device expends 142.26 kJ of energy while pressurizing 3.93 kg of water initially at 12.88°C. The efficiency of the heating device is 59.73%. Inefficiencies are represented by a heat loss from the device casing. Determine the final temperature in °C.
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1) A piston-cylinder system containing 1100 grams of an ideal gas ‘X’ is cooled from 900 K to 100 K at constant pressure. The specific heat capacity of the gas is Cp = 38.3 J.mol-1.K-1. Assume Cp stays constant in the given temperature range. The molar mass of the gas = 28 g.mol-1. a) Write the simplified first law of thermodynamics for this system with justification. b) Calculate the total heat transferred (in kJ) during the process of cooling c) If the entire heat from the cooling of ‘X’ (as calculated in (b)) could be used as work to change the volume of another gas ‘Y’ from 500 m3 to 1000 m3 in a constant pressure process, calculate the value of pressure. d) Instead of cooling at constant pressure, if ‘X’ was expanded reversibly and at a constant temperature (300K), calculate the work done by the system in kJ if the change in volume was 10-fold.