Solving Torque: R=9cm, F=18N, d=30cm

[ohheytai]

what is the torque??

A disk of radius R = 9 cm is pulled along a frictionless surface with a force of F = 18 N by a string wrapped around the edge.


At the instant when d = 30 cm of string has unwound off the disk, what is the torque exerted about the center of the disk?



i tried $$\tau$$ = R*F but it did not work can someone help me?

 

[Doc Al]

i tried $$\tau$$ = R*F but it did not work can someone help me?

Seems right to me. Show exactly what you did.

 

[ohheytai]

i did .09m*18N and got 1.62 N*m but its wrong

 

[Doc Al]

i did .09m*18N and got 1.62 N*m but its wrong

Is the string tangent to the disk or at an angle?

 

[ohheytai]

tangent

 

[Doc Al]

tangent

Then I'd say that you answer is correct.

Post the entire problem including any diagrams.

 

[ohheytai]

okay here it is

 

[Doc Al]

I'd say your answer is correct. The distance is irrelevant.

Is this a stand alone problem or just one part of a longer problem?

 

[ohheytai]

stand alone.

 

[vietsubject]

i did .09m*18N and got 1.62 N*m but its wrong

the answer is <0,0,-1.62> N*m lol :)