Physics EK 1001, Question 352 (and 353)

[SKaminski]

---

Members don't see this ad.

Physics EK 1001: Question 352 (and 353)
352: Which of the following statements is true?
A. No work is done on an object if that object remains stationary. (My answer)
B. Not pertinent (I'm leaving this one out)
C. Energy is conserved when frictional forces are applied to an object. (Credited Answer)
D. Energy transfer as heat always accompanies friction. (Other answer I thought was correct.)

I understand that A is wrong because you can change the internal energy of an object via friction.

I don't understand why D is wrong, unless its as miniscule as there use of the word 'heat'. This is the only answer I can think of, because question 353 makes you assume that when you slide a block over a friction-y table, you get a temperature change in the block, and a temperature change in the table.

Is heat a specific enough word that it warrants this sort of exclusion in my future Process of Elimination?

Text of question 353:

A block slides to a stop along a table top. Which of the following statements is NOT true?

A. The Change in the mechanical energy of the block is equal to the force of friction times the distance that the block slide.
B. The temperature of the block increased.
C. The temperature of the table increased.
D. The temperature change of the table is equal to the temperature change of the block.

D is the credit answer, making it not true. This means that whenever there is friction, there IS TEMPERATURE CHANGE. I can not consolidate this with the previous question (352) unless the words 'heat' and 'temperature' are being used extremely specifically.

What do you guys think?

 

[shoehornlettuce]

Physics EK 1001: Question 352 (and 353)
352: Which of the following statements is true?
A. No work is done on an object if that object remains stationary. (My answer)
B. Not pertinent (I'm leaving this one out)
C. Energy is conserved when frictional forces are applied to an object. (Credited Answer)
D. Energy transfer as heat always accompanies friction. (Other answer I thought was correct.)

I understand that A is wrong because you can change the internal energy of an object via friction.

I don't understand why D is wrong, unless its as miniscule as there use of the word 'heat'. This is the only answer I can think of, because question 353 makes you assume that when you slide a block over a friction-y table, you get a temperature change in the block, and a temperature change in the table.

Is heat a specific enough word that it warrants this sort of exclusion in my future Process of Elimination?

Text of question 353:

A block slides to a stop along a table top. Which of the following statements is NOT true?

A. The Change in the mechanical energy of the block is equal to the force of friction times the distance that the block slide.
B. The temperature of the block increased.
C. The temperature of the table increased.
D. The temperature change of the table is equal to the temperature change of the block.

D is the credit answer, making it not true. This means that whenever there is friction, there IS TEMPERATURE CHANGE. I can not consolidate this with the previous question (352) unless the words 'heat' and 'temperature' are being used extremely specifically.

What do you guys think?

Heat and Temperature are NOT the same thing. Heat is a measure of energy (units = joules). Temperature is a measure of hot or cold (units = degrees fahrenheit, celcius, kelvin). I'm assuming for the first question they are referring to conservation of energy. Within a system energy can change form but it isn't created or destroyed.

For the second question, think about the size of the objects. For example, if you try to boil an ounce of water over a stove, it will start to boil in a few seconds. Now say you are trying to boil several gallons of water using the same stove at the same temperature. It will take several minutes. Even though the same amount of energy (i.e. heat) is going into the block as is the table, the block will have a lower temperature.

 

[silverice]

I still don't understand 352. Please help.

 

[slz1900]

I think D is right too. Friction always converts kinetic energy into heat. There are a lot of mistakes in examkrackers, so this might be another one.

 

[silverice]

I agree that there're a lot of mistakes in ek and frustrates me.