Sign Up For Free

**Join for FREE**,
and start talking with other members, weighing in on community discussions,
and more.

Also, by registering and logging in you'll see fewer ads and pesky welcome messages (like this one!)

- Reply to threads, and start your own.
- Post reviews of your campus visits.
- Find hundreds of pages of informative articles.
- Search from over 3 million scholarships.

College Confidential’s “Dean,” Sally Rubenstone, put together 25 of her best tips. So far, the "25 Tips from the Dean" eBook has helped more than 10K students choose a college, get in, and pay for it. Get your free copy: http://goo.gl/9zDJTM

Xylem101
Registered User Posts: **868** Member

I saw a question that asked to give an example of friction doing +ve Work, how is this possible and Give me an example if it is...

Post edited by Xylem101 on

This discussion has been closed.

## Replies to: Can Friction do Positive WorK?

743Member172Junior Member868Member9,265Super Moderator1,313Senior Memberxylem: force of friction is in the opposite direction of the motion... so if you move a block to the right (+) friction does - work... if you move the block to the left (-) the friction does + work

80Junior Memberwhen you sum the forces, friction is a negative force because postitive forces are in direction of motion. theta is the angle between friction and r, your displacement. Since friction is in the direction opposite displacement, theta= 180 and work is thus negative. Therefore, friction always does negative work.

1,313Senior Member80Junior MemberAnother way of looking at it is with the equation Work=magnitude of friction*magnitude of r*cos180. In this equation, you only look at the MAGNITUDES of friction and r, which are always positive. In this case, cos 180 gives you the negative sign and Work done by friction is still negative.

The cos 180 tells you that friction is always opposite the direction of displacement.

1,313Senior Member268Junior Member1,975Senior Member124Junior Member1,084Senior Member