Question 1
A block of aluminum is heated to 172 degrees on a hot plate. If we consider room temperature
to be 25 degrees C, what is the excess temperature of this block?
197 degrees C
100 degrees C
172 degrees C
25 degrees C
147 degrees C
Question 2
True of False:
The smaller the value of time constant the faster the object cools off.
True
False
Question 3
What is the limiting value of all excess temperature as time goes to infinity?
zero
0 degrees Kelvin
infinity
25 degrees C
0 degrees C
Question 4
A block of steel is cooling off from a high temperature. What will be the effect on the time
constant if suddenly a fan is directed towards the block?
The time constant will rise in value
The time constant will not change
The time constant will drop in value
No answer text provided.
Question 5
A block of steel has a thermal cooling time constant (Tau) of 3500 seconds. It starts out at 300
degrees C as read by a digital thermometer placed on the block. Room temperature is 25 degrees
C. After 3000 seconds determine the temperature of the block as measured by a digital
thermometer.
109.3 degrees C as measured by a digital thermometer.
133.6 degrees C as measured by a digital thermometer.
115.1 degrees C as measured by a digital thermometer. 141.7 degrees C as measured by a digital thermometer
128.4 degrees C as measured by a digital thermometer.
Question 6
The large swimming pool at the Hanington estate has a thermal cooling time constant (Tau) of 12
days. How long will it take for the water temperature to drop from 40 degrees C to 30 degrees C?
Answer in days. These are actual temperatures being measured by a digital thermometer. You can
assume that the outdoor temperature stays constant at 25 degrees C day and night for this
problem.
8.5 days to get to the final cooler temperature
9.7 days to get to the final cooler temperature
11.4 days to get to the final cooler temperature
13.2 days to get to the final cooler temperature
10.3 days to get to the final cooler temperature
Question 7
What is the thermal cooling time constant (Tau) for an engine in a car if the car cools down from
115 degrees C to 35 degrees C in 2 hours. Give the answer in hours for that time constant. The
temperatures given are actual temperatures as measured by a digital thermometer and you can
assume that outside temperature is a constant 25 degrees C.
1.13 hours
1.58 hours
1.49 hours
0.91 hours
1.73 hours
Question 8
Determine the thermal cooling time constant (Tau) for a block of copper using the following
actual temperature data as measured by a digital thermometer inserted into the block. Room
temperature is 25 degrees C:
Initial hot temperature:155 degrees C
Temperature after 300 seconds:100 degreesC
Your time constant units should be in seconds.
623 seconds
594 seconds
545 seconds 413 seconds
Question 9
When Melvin Purvis was chasing John Dillinger in 1934, he came upon a camp fire made by the
notorious bank robber some time before. He spotted the smoldering fire remnants at 12:00 noon.
He called in some FBI scientists who determined when the fire was put out and said that
Dillinger was somewhere in the area on foot (there were no car tracks found). Using the data that
the thermal cooling time constant for a typical camp fire of the wood used is Tau = 0.45 hours,
and the smoldering wood had a final temperature of 207 degrees C, and that a typical fire has a
maximum temperature of 1025 degrees C, how far was Dillinger from the camp? Assume that he
can travel 1.75 miles per hour on foot. Give the answer in miles. The values of temperature are
actual temperatures as measured by a mercury thermometer (they did not have digital ones in
1934). Assume the outdoor temperature was 25 degrees C.
1.67 miles away
1.48 miles away
2.45 miles away
1.82 miles away
1.34 miles away
2.16 miles away
2.73 miles away
1.21 miles away
4.05 miles away
3.14 miles away
Question 10
Frank was the blacksmith in old Centerville back in 1921. This was before cars became popular
in that neck of the woods. He was trying to teach his son the trade but it was an uphill battle all
the way. One day for example, as he was showing young Sidney how to fashion a horseshoe, he
spit on the ground while pulling a red hot horseshoe from the yellow coal fire and began beating
it into shape, instructing his son that "...you gotta hurry and have no draft...after one minute the
temperature of the metal drops to 700 degrees Celsius but if you don't have the shop doors closed
the temperature would be at only 400 degrees Celsius because the time constant in the windy
situation is decreased BY exactly 2.806 minutes (so said that professor fella) and the metal cools
off faster and 400 degrees Celsius ain't no good to fashion a good horse shoe....". Sadly, Sidney
was only interested in the new Hollywood magazines and never really wanted to become a
blacksmith and since he was constantly thinking of Serina next door, he couldn't care less.
Help Sidney out and determine the time constant of the metal with the shop doors are closed.
The units of the time constant should be in minutes.
4.00 minutes
6.04 minutes 4.257 minutes
8.50 minutes
8.35 minutes
7.25 minutes
1.44 minutes
3.02 minutes
5.57 minutes
6.93 minutes
5.500 minutes
7.51 minutes
5.00 minutes
3.00 minutes

 

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Status NEW Posted 20 Apr 2017 04:04 AM My Price 15.00

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