PHYSICS CHAPTER 1,2,3
What does it mean to say that two systems are in thermal equilibrium?
- when two bodies are in contact with each other and *can freely exchange energy. * -when they have the same temperature.
Give an example of a physical property that varies with temperature and describe how it is used to measure temperature.
-volume, basis for alcohol thermometers -electrical resistance, color and emission of infrared radiation
The brakes in a car increase in temperature by ΔT when bringing the car to rest from a speed v. How much greater would ΔT be if the car initially had twice the speed? You may assume the car stops fast enough that no heat transfers out of the brakes.
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One method of getting a tight fit, say of a metal peg in a hole in a metal block, is to manufacture the peg slightly larger than the hole. The peg is then inserted when at a different temperature than the block. Should the block be hotter or colder than the peg during insertion?Explain your answer.
Hotter than the peg because if we increase the temperature we increase the volume which will increase the size of the hole
Pouring cold water into hot glass or ceramic cookware can easily break it. What causes the breaking? Explain why Pyrex®, a glass with a small coefficient of linear expansion, is less susceptible.
The cold water cools part of the inner surface, making it contract, while the rest remains expanded. The strain is too great for the strength of the material. Pyrex contracts less, so it experiences less strain.
If a thermometer is allowed to come to equilibrium with the air, and a glass of water is not in equilibrium with the air,what will happen to the thermometer reading when it is placed in the water?
The reading will change.
How is heat transfer related to temperature?
heat transfer is a result of difference in temperature
Describe a situation in which heat transfer occurs.
heating, cooking
When a cold alcohol thermometer is placed in a hot liquid, the column of alcohol goes down slightly before going up. Explain why.
the volume of the glass instantly increases when it enters a hotter temperature, therefore expanding the glass thermometer, this in turn decreases the column of the glass because the amount stays the same when the volume increases
Does it really help to run hot water over a tight metallid on a glass jar before trying to open it?Explain your answer.
yes when you run hot water over it it allows the glass jar lid to expand making it larger than the actual size of the lid, making it easier to open the jar.
