4. A. In class we discussed the fact that we can heat water quite efficiently by

Question

4. A. In class we discussed the fact that we can heat water quite efficiently by use of a microwave oven. A cup or glass (that holds the water) will not generally heat up if it is in the microwave, but empty. An important reason that the cup gets hot when water is in it and the microwaves are turned on is that a. it does not, it is just your imagination b. the water is heated and the cup or glass is heated by conduction c. the infrared from the microwaves heats the cup d. convection of the heated water does the heating e. none of the above 4. B. You take a glass jar full of pickles out of your refrigerator. You find that you don't have enough stgrength to twist off the cap that is screwed on to the glass jar. Why will running the cap under hot water for a minute or so make the cap easier to get off? a. it makes the metal cap shrink b. it make the glass expand c. the glass expands more than the metal cap d. the metal cap expands more than the glass e. none of the above 5. A 2000 kg truck moving at 25 m/sec is stopped by the brakes. What is the kinetic energy of the moving truck? If the brakes are made out of steel (four disk brakes, each of mass 4 kg), and all the energy of the moving truck is converted to heat when the brakes stop the truck, what will the temperature change of the brakes be? (You may presume no heat is lost to the environment in the process. This is not a great assumption here, but it does result in a worst-case temperature change for the brakes - a number good to have if you are the person who is designing the brakes and you are worried about the worst case.) 6. A. A wood burning stove sits in the family room of a house and there is a fire in the stove to help heat the room Of those listed here, which mechanisms are primarily at work to heat the room. Pick the most important two of these. a. radiation b. convection c. conduction d. vaporization e. microwaves

Explanation / Answer

Question 4A

Answer : Option B

Question 4B

Answer : Option D

Reason : The metal expands more as compared to glass. So upon heating the cap will lose its grip on glass and it will become loose.

Related Questions

Navigate

• Browse (All)
• Browse 4
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.