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free/or 0.5$ |
| 55483 | A thermal window with an area of 6.00 m2 is constructed of two layers of glass, each 4.00 mm thick, and separated from each other by an air space of 5.00 mm. If the inside surface is at 20.0°C and the outside is at - 30.0°C, what is the rate of energy transfer by conduction through the window? |
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| 55484 | The yellow caution light on a traffic signal should stay on long enough to allow a driver to either pass through the intersection or safely stop before reaching the intersection. A car can stop if its distance from the intersection is greater than the stopping distance found in the previous problem. If the car is less than this stopping distance from the intersection, the yellow light should stay on long enough to allow the car to pass entirely through the intersection.
(a) Show that the yellow light should stay on for a time interval ∆ttight = ∆t r – (vo / 2a) + (si / vo) Where ∆tr is the driver’s reaction time, v0 is the velocity of the car approaching the light at the speed limit, a is the braking acceleration, and si is the width of the intersection.
(b) As city traffic planner, you expect cars to approach an intersection 16.0 m wide with a speed of 60.0 km/h. Be cautious and assume a reaction time of 1.10 s to allow for a driver’s indecision. Find the length of time the yellow light should remain on. Use a braking acceleration of - 2.00 m/s2. |
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| 55485 | The void fraction of a porous medium is the ratio of the void volume to the total volume of the material. The void is the hollow space within the material; it may be filled with a fluid. A cylindrical canister of diameter 2.54 cm and height 20.0 cm is filled with activated carbon having a void fraction of 0.765. Then it is flushed with an ideal gas at 25.0°C and pressure 12.5 atm. How many moles of gas are contained in the cylinder at the end of this process? |
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| 55486 | The uniform beam has a weight of 5000 lb. Determine the average tension in each of the two cables AB and AC if the beam is given an upward speed of 8 ft/s in 1.5 s starting from rest. Neglect the mass of the cables. |
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| 55487 | The U.S. penny was formerly made mostly of copper and is now made of copper-coated zinc. Can a calorimetric experiment be devised to test for the metal content in a collection of pennies? If so, describe the procedure you would use. |
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| 55488 | The twitch in a muscle of the arm develops a force which can be measured as a function of time as shown in the graph. If the effective contraction of the muscle lasts for a time t0, determine the impulse developed by the muscle. |
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| 55489 | The tungsten filament of a certain 100-W light bulb radiates 2.00 W of light. (The other 98 W is carried away by convection and conduction.) The filament has a surface area of 0.250 mm2 and an emissivity of 0.950. Find the filament’s temperature. (The melting point of tungsten is 3 683 K.) |
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| 55490 | The temperature of a silver bar rises by 10.0°C when it absorbs 1.23 kJ of energy by heat. The mass of the bar is 525 g. Determine the specific heat of silver. |
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| 55491 | The temperature difference between the inside and the outside of an automobile engine is 450°C. Express this temperature difference on (a) The Fahrenheit scale and (b) The Kelvin scale. |
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| 55492 | The temperature at the surface of the Sun is approximately 5 700 K, and the temperature at the surface of the Earth is approximately 290 K. What entropy change occurs when 1 000 J of energy is transferred by radiation from the Sun to the Earth? |
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| 55493 | The surface of the Sun has a temperature of about 5 800 K. The radius of the Sun is 6.96 X 108 m. Calculate the total energy radiated by the Sun each second. Assume that the emissivity of the Sun is 0.965. |
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| 55494 | The speed of sound in air is 331 m/s. During the next thunderstorm, try to estimate your distance from a lightning bolt by measuring the time lag between the flash and the thunderclap. You can ignore the time it takes for the light flash to reach you. Why? |
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| 55495 | The speed of a bullet as it travels down the barrel of a rifle toward the opening is given by v = (- 5.00 x 107)t 2 + (3.00 x 105)t, where v is in meters per second and t is in seconds. The acceleration of the bullet just as it leaves the barrel is zero.
(a) Determine the acceleration and position of the bullet as a function of time when the bullet is in the barrel.
(b) Determine the length of time the bullet is accelerated.
(c) Find the speed at which the bullet leaves the barrel.
(d) What is the length of the barrel? |
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| 55496 | The shore of the ocean is very rocky at a particular place. The rocks form a cave sloping upward from an underwater opening, as shown in Figure Q19.13a. (a) Inside the cave is falls with the tides, , will the level of water in the cave rise and fall? If so, will it have the same amplitude as that of the ocean? (b) What If? Now suppose that the cave is deeper in the water, so that it is completely submerged and filled with water at high tide, as shown in Figure Q19.13b. At low tide, will the level of the water in the cave be the same as that of the ocean? |
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| 55497 | The rocket sled has a mass of 3 Mg and starts from rest when t = 0. If the engines provide a horizontal thrust T which varies as shown in the graph, determine the sled’s velocity in t = 4 s. Neglect air resistance, friction, and the loss of fuel during the motion. |
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| 55498 | The relationship Lf = Li (1 + αΔT) is an approximation that works when the average coefficient of expansion is small. If α is large, one must integrate the relationship dL/dT =αL to determine the final length. (a) Assuming that the coefficient of linear expansion is constant as L varies, determine a general expression for the final length. (b) Given a rod of length 1.00 m and a temperature change of 100.0°C, determine the error caused by the approximation when α = 2.00 X 10-5 (°C)-1 (a typical value for a metal) and when & = 0.020 0 (°C)-1 (an unrealistically large value for comparison). |
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| 55499 | The rectangular plate shown in Figure P19.55 has an area Ai equal to If the temperature increases by ΔT, each dimension increases according to the equation ΔL = aLi ΔT, where & is the average coefficient of linear expansion. Show that the increase in area is ΔA = 2aAi ΔT. What approximation does this expression assume? |
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| 55500 | As indicated by the derivation, the principle of impulse and momentum is valid for observers in any inertial reference frame. Show that this is so, by considering the 10-kg block which rests on the smooth surface and is subjected to a horizontal force of 6 N. If observer A is in a fixed frame x, determine the final speed of the block in 4 s if it has an initial speed of 5 m/s measured from the fixed frame. Compare the result with that obtained by an observer B, attached to the x’ axis that moves at a 6 constant velocity of 2 m/s relative to A. |
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| 55501 | The pressure gauge on a tank registers the gauge pressure, which is the difference between the interior and exterior pressure. When the tank is full of oxygen (O2), it contains 12.0 kg of the gas at a gauge pressure of 40.0 atm. Determine the mass of oxygen that has been withdrawn from the tank when the pressure reading is 25.0 atm. Assume that the temperature of the tank remains constant. |
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| 55502 | The position versus time for a certain particle moving along the x axis is shown in Figure P2.3. Find the average velocity in the time intervals
(a) 0 to 2 s,
(b) 0 to 4 s,
(c) 2 s to 4 s,
(d) 4 s to 7 s,
(e) 0 to 8 s |
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