Can Friction Cause Torque & Work on Rolling Objects?

[kolua]

can kinetic friction cause a torque? (can it result in rotation)
Or is it that only static friction can cause a torque?

Can static friction do work on a rolling object?
I think it can? because the rotational kinetic energy is increasing? is this right?
HELP!

 

[JBA]

First question response: Ask your self "what is the result of friction?" and "what does it take to create torque?" and you should see the answer to your question.

Second question response: The answer to the first question should let you know if the second statement is true.

 

[BvU]

can kinetic friction cause a torque? (can it result in rotation)
Or is it that only static friction can cause a torque?

Yes it can: if the line of action of the friction force doesn't go through the center of mass, then that force represents a torque.

Can static friction do work on a rolling object?
I think it can? because the rotational kinetic energy is increasing? is this right?
HELP!

Yes it can: if the object is sliding and rolling you can have what you describe. So in exercises the term "rolling without sliding" may appear to exclude that.

[edit]JBA was faster !

 

[JBA]

Your are right in both of your answers except wrong in your statement about "static" friction applying to sliding while rolling, because that is kinetic friction; which, can also create torque and rotation while sliding.