7. A metal bar at a temperature of 950 °C is placed in a room at a constant temperature of 25 °C. After 20 minutes the bar is 500 °C; find (a) the time for the bar to reach a temperature of 120 °C and (b) the temperature of the bar after 110 minutes. lb roast initially at 50 °E is placed in a 375 °F
7. A metal bar at a temperature of 950 °C is placed in a room at a constant temperature of 25 °C. After 20 minutes the bar is 500 °C; find (a) the time for the bar to reach a temperature of 120 °C and (b) the temperature of the bar after 110 minutes. lb roast initially at 50 °E is placed in a 375 °F
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NEWTON’S LAW OF COOLING AND HEATING
![7. A metal bar at a temperature of 950 °C is placed in a
room at a constant temperature of 25 °C. After 20
minutes the bar is 500 °C; find (a) the time for the bar
to reach a temperature of 120 °C and (b) the
temperature of the bar after 110 minutes.
8. A 4-lb roast, initially at 50 °F, is placed in a 375 °F
oven at 5:00 P.M. After 75 minutes it is found that the
temperature of the roast is 125°F. When will the roast
be 150 °F?
9. A thermometer reading 70°F is placed in an oven
preheated to a constant temperature. Through a glass
window in the oven door, an observer records that the
thermometer reads 110°F after minute and 145°F
[7:02 PM]
after 1 minute. How hot is the oven?
Answer: T= 390°F
10. A thermometer is removed from a room where the
temperature is 70°F and is taken outside, where the
air temperature is 10°F. After one-half minute the
thermometer reads 50°F. What is the reading of the
thermometer at t 1 min? How long will it take for the
thermometer 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 taken
outside where the air temperature is 60°F. At 2:05
PM, the temperature reading yielded by the
thermometer is 70°F. Later, the thermometer is
brought inside where the air is 98°F. At 2:10 PM, the
reading is 89.5°F. Determine when was the
thermometer brought indoor.
12. For obvious reasons", the dissecting-room of a
certain coroner is kept very cool at a constant
temperature of 10°C. While doing an autopsy early
one morning on a murder victim, the coroner himself
is killed and the victim's body is stolen. At 9:40 A.M.
the coroner's assistant discovers his chief's body and
finds its temperature to be 25°C, and at noon the
body's temperature is down to 18°C. Assuming the
coroner had a normal temperature of 37°C when he
was alive, at what time was he murdered?](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa79fb729-837c-460f-9786-c3be4511de53%2Ffc08815b-7878-4607-a93a-79ebe169405e%2Fa8fe7d_processed.png&w=3840&q=75)
Transcribed Image Text:7. A metal bar at a temperature of 950 °C is placed in a
room at a constant temperature of 25 °C. After 20
minutes the bar is 500 °C; find (a) the time for the bar
to reach a temperature of 120 °C and (b) the
temperature of the bar after 110 minutes.
8. A 4-lb roast, initially at 50 °F, is placed in a 375 °F
oven at 5:00 P.M. After 75 minutes it is found that the
temperature of the roast is 125°F. When will the roast
be 150 °F?
9. A thermometer reading 70°F is placed in an oven
preheated to a constant temperature. Through a glass
window in the oven door, an observer records that the
thermometer reads 110°F after minute and 145°F
[7:02 PM]
after 1 minute. How hot is the oven?
Answer: T= 390°F
10. A thermometer is removed from a room where the
temperature is 70°F and is taken outside, where the
air temperature is 10°F. After one-half minute the
thermometer reads 50°F. What is the reading of the
thermometer at t 1 min? How long will it take for the
thermometer 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 taken
outside where the air temperature is 60°F. At 2:05
PM, the temperature reading yielded by the
thermometer is 70°F. Later, the thermometer is
brought inside where the air is 98°F. At 2:10 PM, the
reading is 89.5°F. Determine when was the
thermometer brought indoor.
12. For obvious reasons", the dissecting-room of a
certain coroner is kept very cool at a constant
temperature of 10°C. While doing an autopsy early
one morning on a murder victim, the coroner himself
is killed and the victim's body is stolen. At 9:40 A.M.
the coroner's assistant discovers his chief's body and
finds its temperature to be 25°C, and at noon the
body's temperature is down to 18°C. Assuming the
coroner had a normal temperature of 37°C when he
was alive, at what time was he murdered?
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