NEWTON’S LAW OF COOLING AND HEATING 7. A metal bar at a temperature of 950 °C is placed in aroom at a constant temperature of 25 °C. After 20minutes the bar is 500 °C; find (a) the time for the barto reach a temperature of 120 °C and (b) thetemperature of the bar after 110 minutes.8. A 4-lb roast, initially at 50 °F, is placed in a 375 °Foven at 5:00 P.M. After 75 minutes it is found that thetemperature of the roast is 125°F. When will the roastbe 150 °F?9. A thermometer reading 70°F is placed in an ovenpreheated to a constant temperature. Through a glasswindow in the oven door, an observer records that thethermometer reads 110°F after minute and 145°F[7:02 PM]after 1 minute. How hot is the oven?Answer: T= 390°F10. A thermometer is removed from a room where thetemperature is 70°F and is taken outside, where theair temperature is 10°F. After one-half minute thethermometer reads 50°F. What is the reading of thethermometer at t 1 min? How long will it take for thethermometer to reach 15°F?Answer: 7(1) = 36.67°F, and t = 3.06 min)11. At 2:00 PM, a thermometer reading 98°F is takenoutside where the air temperature is 60°F. At 2:05PM, the temperature reading yielded by thethermometer is 70°F. Later, the thermometer isbrought inside where the air is 98°F. At 2:10 PM, thereading is 89.5°F. Determine when was thethermometer brought indoor.12. For obvious reasons", the dissecting-room of acertain coroner is kept very cool at a constanttemperature of 10°C. While doing an autopsy earlyone morning on a murder victim, the coroner himselfis killed and the victim's body is stolen. At 9:40 A.M.the coroner's assistant discovers his chief's body andfinds its temperature to be 25°C, and at noon thebody's temperature is down to 18°C. Assuming thecoroner had a normal temperature of 37°C when hewas alive, at what time was he murdered?

As per guidelines, only first question is solved here.

Answered: 7. A metal bar at a temperature of 950…

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter11: Energy In Thermal Processes

Section: Chapter Questions

Problem 49P: A copper rod and an aluminum rod of equal diameter are joined end to end in good thermal contact....

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1. How much heat is conducted in one hour through an iron plate 2.0 cm thick and 100 cm2 in area, the temperature of the two sides being kept at 0 and 20°C? 2. A nickel plate 0.8 cm thick has a temperature difference of 64°C between its faces. It transmits 200kcal/hr through an area of 10cm2. Calculate the thermal conductivity of nickel in cgs units. 3. A container used to store ice is made of wood 5.0 cm thick and has an effective area of 12,000 cm2 and thermal conductivity of 0.00027 cal/cm2-sec-°C/cm. How much ice inside the box would be melted each 24-hour day if the outside temperature is 25°C and the temperature inside the box is 5°C.
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