Conservative force vs nonConservative force

1. Nov 5, 2007

jack1234

In a given displacement of a particle, its kinetic energy increases by 25 J while its potential energy decreases by 10 J. Determine the work of the nonconservative forces acting on the particle during this displacement.
a. –15 J b. +35 J c. +15 J d. –35 J e. +55 J

workdone by non-conservative force
=change in mechanical energy
=25-10
=15

Hence I expect the answer to be c, but it turns up to be a, what is the reason?

Last edited: Nov 5, 2007
2. Nov 5, 2007

learningphysics

I agree with you. It should be c) +15J.

3. Nov 13, 2008