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engineering
mechanical engineering
Questions and Answers of
Mechanical Engineering
In moving out of a dormitory at the end of the semester, a student does 1.6 × 104 J of work. In the process, his internal energy decreases by 4.2 × 104 J. Determine each of the following quantities
A system gains 2780 J of heat at a constant pressure of 1.26 × 105 Pa, and its internal energy increases by 3990 J. What is the change in the volume of the system, and is it an increase or a
Beginning with a pressure of 2.20 × 105 Pa and a volume of 6.34 × 10-3 m3, an ideal monatomic gas (γ = 5/3) undergoes an adiabatic expansion such that its final pressure is 8.15 × 104 Pa. An
An ideal, or Carnot, heat pump is used to heat a house to a temperature of 294 K (21 °C). How much work must the pump do to deliver 3350 J of the heat into the house on a day when the outdoor
The sublimation of zinc (mass per mole = 0.0654 kg/mol) takes place at a temperature of 6.00 × 102 K, and the latent heat of sublimation is 1.99 × 106 J/kg. The pressure remains constant ∆U ring
Each of two Carnot engines uses the same cold reservoir at a temperature of 275 K for its exhaust heat. Each engine receives 1450 J of input heat. The work from either of these engines is used to
A system gains 1500 J of heat, while the internal energy of the system increases by 4500 J and the volume decreases by 0.010 m3. Assume that the pressure is constant and find its value?
The volume of a gas is changed along the curved line between A and B in the drawing. Do not assume that the curved line is an isotherm or that the gas is ideal.(a) Find the magnitude of the work for
A gas is contained in a chamber such as that in Figure 15.4. Suppose that the region outside the chamber is evacuated and the total mass of the block and the movable piston is 135 kg. When 2050 J of
A piece of aluminum has a volume of 1.4 × 10-3 m3. The coefficient of volume expansion for aluminum is β = 69 × 10-6 (Co)-1. The temperature of this object is raised from 20 to 320 oC. How much
Refer to Multiple-Concept Example 3 to see how the concepts pertinent to this problem are used. The pressure of a gas remains constant while the temperature, volume, and internal energy of the gas
Refer to the drawing that accompanies Problem 13. When a system changes from A to B along the path shown on the pressure-versus-volume graph, it gains 2700 J of heat. What is the change in the
Water is heated in an open pan where the air pressure is one atmosphere. The water remains a liquid, which expands by a small amount as it is heated. Determine the ratio of the work done by the water
The internal energy of a system changes because the system gains 165 J of heat and performs 312 J of work. In returning to its initial state, the system loses 114 J of heat. During this return
Six grams of helium (molecular mass = 4.0 u) expand isothermally at 370 K and does 9600 J of work. Assuming that helium is an ideal gas, determine the ratio of the final volume of the gas to the
Three moles of neon expand isothermally to 0.250 from 0.100 m3. Into the gas flows 4.75 × 103 J of heat. Assuming that neon is an ideal gas, find its temperature?
The temperature of a monatomic ideal gas remains constant during a process in which 4700 J of heat flows out of the gas. How much work (including the proper + or - sign) is done?
One-half mole of a monatomic ideal gas expands adiabatically and does 610 J of work. By how many kelvins does its temperature change? Specify whether the change is an increase or a decrease.
Heat is added isothermally to 2.5 mol of a monatomic ideal gas. The temperature of the gas is 430 K. How much heat must be added to make the volume of the gas double?
A diesel engine does not use spark plugs to ignite the fuel and air in the cylinders. Instead, the temperature required to ignite the fuel occurs because the pistons compress the air in the
A monatomic ideal gas expands from point A to point B along the path shown in the drawing.(a) Determine the work done by the gas.(b) The temperature of the gas at point A is 185 K. What is its
A monatomic ideal gas (γ = 5/3) is contained within a perfectly insulated cylinder that is fitted with a movable piston. The initial pressure of the gas is 1.50 × 105 Pa. The piston is pushed so as
The pressure and volume of an ideal monatomic gas change from A to B to C, as the drawing shows. The curved line between A and C is an isotherm.(a) Determine the total heat for the process and(b)
The work done by one mole of a monatomic ideal gas (γ = 5/3) in expanding adiabatically is 825 J. The initial temperature and volume of the gas are 393 K and 0.100 m3. Obtain (a) The final
Argon is a monatomic gas whose atomic mass is 39.9 u. The temperature of eight grams of argon is raised by 75 K under conditions of constant pressure. Assuming that argon behaves as an ideal gas, how
Under constant-volume conditions, 3500 J of heat is added to 1.6 moles of an ideal gas. As a result, the temperature of the gas increases by 75 K. How much heat would be required to cause the same
A monatomic ideal gas in a rigid container is heated from 217 K to 279 K by adding 8500 J of heat. How many moles of gas are there in the container?
Three moles of a monatomic ideal gas are heated at a constant volume of 1.50 m3. The amount of heat added is 5.24 × 103 J. (a) What is the change in the temperature of the gas? (b) Find the change
A system does 4.8 × 104 J of work, and 7.6 × 104 J of heat flows into the system during the process. Find the change in the internal energy of the system?
A monatomic ideal gas expands at constant pressure. (a) What percentage of the heat being supplied to the gas is used to increase the internal energy of the gas? (b) What percentage is used for doing
Suppose a monatomic ideal gas is contained within a vertical cylinder that is fitted with a movable piston. The piston is frictionless and has a negligible mass. The area of the piston is 3.14 ×
A monatomic ideal gas is heated while at a constant volume of 1.00 × 10-3 m3, using a ten-watt heater. The pressure of the gas increases by 5.0 × 104 Pa. How long was the heater on?
One mole of neon, a monatomic gas, starts out at conditions of standard temperature and pressure. The gas is heated at constant volume until its pressure is tripled, then further heated at constant
Multiple-Concept Example 6 provides a review of the concepts that play roles here. An engine has an efficiency of 64% and produces 5500 J of work. Determine (a) The input heat and (b) The rejected
Engine 1 has an efficiency of 0.18 and requires 5500 J of input heat to perform a certain amount of work. Engine 2 has an efficiency of 0.26 and performs the same amount of work. How much input heat
Due to a tune-up, the efficiency of an automobile engine increases by 5.0%. For an input heat of 1300 J, how much more work does the engine produce after the tune-up than before?
A 52-kg mountain climber, starting from rest, climbs a vertical distance of 730 m. At the top, she is again at rest. In the process, her body generates 4.1 × 106 J of energy via metabolic processes.
In a game of football outdoors on a cold day, a player will begin to feel exhausted after using approximately 8.0 × 105 J of internal energy. (a) One player, dressed too lightly for the weather, has
Engine A receives three times more input heat, produces five times more work, and rejects two times more heat than engine B. Find the efficiency of (a) Engine A and (b) Engine B?
A Carnot engine operates with an efficiency of 27.0% when the temperature of its cold reservoir is 275 K. Assuming that the temperature of the hot reservoir remains the same, what must be the
An engine has a hot-reservoir temperature of 950 K and a cold-reservoir temperature of 620 K. The engine operates at three-fifths maximum efficiency. What is the efficiency of the engine?
A Carnot engine operates with a large hot reservoir and a much smaller cold reservoir. As a result, the temperature of the hot reservoir remains constant while the temperature of the cold reservoir
An engine does 18 500 J of work and rejects 6550 J of heat into a cold reservoir whose temperature is 285 K. What would be the smallest possible temperature of the hot reservoir?
A Carnot engine has an efficiency of 0.40. The Kelvin temperature of its hot reservoir is quadrupled, and the Kelvin temperature of its cold reservoir is doubled. What is the efficiency that results
A Carnot engine operates between temperatures of 650 and 350 K. To improve the efficiency of the engine, it is decided either to raise the temperature of the hot reservoir by 40 K or to lower the
The hot reservoir for a Carnot engine has a temperature of 890 K, while the cold reservoir has a temperature of 670 K. The heat input for this engine is 4800 J. The 670-K reservoir also serves as the
Suppose that the gasoline in a car engine burns at 631 oC, while the exhaust temperature (the temperature of the cold reservoir) is 139 oC and the outdoor temperature is 27 oC. Assume that the engine
A power plant taps steam superheated by geothermal energy to 505 K (the temperature of the hot reservoir) and uses the steam to do work in turning the turbine of an electric generator. The steam is
A nuclear-fueled electric power plant utilizes a so-called "boiling water reactor." In this type of reactor, nuclear energy causes water under pressure to boil at 285 oC (the temperature of the hot
The inside of a Carnot refrigerator is maintained at a temperature of 277 K, while the temperature in the kitchen is 299 K. Using 2500 J of work, how much heat can this refrigerator remove from its
A refrigerator operates between temperatures of 296 and 275 K. What would be its maximum coefficient of performance?
Two Carnot air conditioners, A and B, are removing heat from different rooms. The outside temperature is the same for both rooms, 309.0 K. The room serviced by unit A is kept at a temperature of
The water in a deep underground well is used as the cold reservoir of a Carnot heat pump that maintains the temperature of a house at 301 K. To deposit 14 200 J of heat in the house, the heat pump
A Carnot engine has an efficiency of 0.55. If this engine were run backward as a heat pump, what would be the coefficient of performance?
A Carnot refrigerator is used in a kitchen in which the temperature is kept at 301 K. This refrigerator uses 241 J of work to remove 2561 J of heat from the food inside. What is the temperature
The wattage of a commercial ice maker is 225 W and is the rate at which it does work. The ice maker operates just like a refrigerator or an air conditioner and has a coefficient of performance of
Review Conceptual Example 9 before attempting this problem. A window air conditioner has an average coefficient of performance of 2.0. In a futile attempt to cool a bedroom, this unit has been placed
How long would a 3.00-kW space heater have to run to put into a kitchen the same amount of heat as a refrigerator (coefficient of performance = 3.00) does when it freezes 1.50 kg of water at 20.0 °C
A Carnot refrigerator transfers heat from its inside (6.0 °C) to the room air outside (20.0 °C). (a) Find the coefficient of performance of the refrigerator. (b) Determine the magnitude of the
A Carnot engine uses hot and cold reservoirs that have temperatures of 1684 and 842 K, respectively. The input heat for this engine is |QH|. The work delivered by the engine is used to operate a
Consider three engines that each use 1650 J of heat from a hot reservoir (temperature = 550 K). These three engines reject heat to a cold reservoir (temperature = 330 K). Engine I rejects 1120 J of
Heat Q flows spontaneously from a reservoir at 394 K into a reservoir at 298 K. Because of the spontaneous flow, 2800 J of energy is rendered unavailable for work when a Carnot engine operates
On a cold day, 24 500 J of heat leaks out of a house. The inside temperature is 21 °C, and the outside temperature is - 15 °C. What is the increase in the entropy of the universe that this heat
(a) After 6.00 kg of water at 85.0 °C is mixed in a perfect thermos with 3.00 kg of ice at 0.0 °C, the mixture is allowed to reach equilibrium. When heat is added to or removed from a solid or
A system undergoes a two-step process. In the first step, the internal energy of the system increases by 228 J when 166 J of work is done on the system. In the second step, the internal energy of the
The sun is a sphere with a radius of 6.96 × 108 m and an average surface temperature of 5800 K. Determine the amount by which the sun's thermal radiation increases the entropy of the entire universe
An irreversible engine operates between temperatures of 852 and 314 K. It absorbs 1285 J of heat from the hot reservoir and does 264 J of work. (a) What is the change ∆Suniverse in the entropy of
The pressure of a monatomic ideal gas (γ = 5/3) doubles during an adiabatic compression. What is the ratio of the final volume to the initial volume?
Multiple-Concept Example 6 deals with the same concepts as this problem does. What is the efficiency of a heat engine that uses an input heat of 5.6 × 104 J and rejects 1.8 × 104 J of heat?
A gas, while expanding under isobaric conditions, does 480 J of work. The pressure of the gas is 1.6 × 105 Pa, and its initial volume is 1.5 × 10-3 m3. What is the final volume of the gas?
A lawnmower engine with an efficiency of 0.22 rejects 9900 J of heat every second. What is the magnitude of the work that the engine does in one second?
A process occurs in which the entropy of a system increases by 125 J/K. During the process, the energy that becomes unavailable for doing work is zero. (a) Is this process reversible or
A Carnot heat pump operates between an outdoor temperature of 265 K and an indoor temperature of 298 K. Find its coefficient of performance.
The temperatures indoors and outdoors are 299 and 312 K, respectively. A Carnot air conditioner deposits 6.12 × 105 J of heat outdoors. How much heat is removed from the house?
Carnot engine A has an efficiency of 0.60, and Carnot engine B has an efficiency of 0.80. Both engines utilize the same hot reservoir, which has a temperature of 650 K and delivers 1200 J of heat to
The pressure and volume of a gas are changed along the path ABCA. Using the data shown in the graph, determine the work done (including the algebraic sign) in each segment of the path: (a) A to B,(b)
Refer to the drawing in Problem 12, where the curve between A and B is now an isotherm. An ideal gas begins at A and is changed along the horizontal line from A to C and then along the vertical line
An air conditioner keeps the inside of a house at a temperature of 19.0 °C when the outdoor temperature is 33.0 °C. Heat, leaking into the house at the rate of 10 500 joules per second, is removed
Even at rest, the human body generates heat. The heat arises because of the body's metabolism-that is, the chemical reactions that are always occurring in the body to generate energy. In rooms
Heat flows from a reservoir at 373 K to a reservoir at 273 K through a 0.35-m copper rod with a cross-sectional area of 9.4 × 10-4 m2 (see the drawing). The heat then leaves the 273-K reservoir
A fifteen-watt heater is used to heat a monatomic ideal gas at a constant pressure of 7.60 × 105 Pa. During the process, the 1.40 × 10-3 m3 volume of the gas increases by 25.0%. How long was the
An ideal gas is taken through the three processes (A B, B C, and C A) shown in the drawing. In general, for each process the internal energy U of the gas can
An engine has an efficiency e1. The engine takes input heat of magnitude |QH| from a hot reservoir and delivers work of magnitude |W1|. The heat rejected by this engine is used as input heat for a
Poke a hole in a piece of cardboard and hold the cardboard horizontally in the sunlight (as in Figure 1.6). Note the image of the Sun that is cast below. To convince yourself that the round spot of
Your favorite young relative is wondering whether to join a large and growing group in the community, mainly to make new friends. Your advice is sought. Before replying, you learn that the group's
As you stand on a floor, does the floor exert an upward force against your feet? How much force does it exert? Why aren't you moved upward by this force?
Answer the preceding question for the case where air resistance is not negligible-where air drag affects motion.
Extend Tables 3.2 and 3.3 to include times of fall of 6 to 10 s, assuming no air resistance. Table 3.2 Time of Fall (seconds) _____________Velocity Acquired
Explain to others whether or not a sheet of paper falls more slowly than one that is wadded into a ball.
Upon which will air resistance be greater: a sheet of paper falling or the same sheet of paper wadded into a ball falling at a faster terminal speed?
Suppose you hold a Ping-Pong ball and a golf ball at arm's length and drop them simultaneously. You'll see them hit the floor at about the same time. But, if you drop them off the top of a high
When skydiver Nellie opens her parachute, the air drag pushing the chute upward is stronger than Earth's force of gravity pulling her downward. A friend says this means she should start moving
A rock band's tour bus, mass M, is accelerating away from a stop sign at rate a when a piece of heavy metal, mass M/5, falls onto the top of the bus and remains there. a. Show that the bus's
A regular tennis ball and another filled with lead pellets are dropped at the same time from the top of a building. Which one hits the ground first? Which one experiences greater air resistance?
Betty (mass 40 kg), standing on slippery ice, catches her leaping dog (mass 15 kg) moving horizontally at 3.0 m/s. Show that the speed of Betty and her dog after the catch is about 0.8 m/s?
A railroad diesel engine weighs four times as much as a freight car. If the diesel engine coasts at 5 km/h into a freight car initially at rest, show that the speed of the coupled engine and car is 4
The balls shown have different masses and speeds. Rank the following from greatest to least:a. The momenta. b. The impulses needed to stop the balls?
You jump from a canoe to the nearby dock, expecting an easy landing. Instead, you land in the water. What is your explanation for this mishap?
How can a fully dressed person at rest in the middle of a pond on perfectly frictionless ice get to shore?
In a movie, the hero jumps straight down from a bridge onto a small boat that continues to move with no change in velocity. What physics is being violated here? Discuss.
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