If the resultant of all the external forces acting on a system of particles is zero, then from an inertial frame, one can suresly say that
A) linear momentum of the system does not change in time
B) Kinetic energy of the system does not change in time
C) angular momentum of the system does not change in time
D) potential energy of the system does not change in time.
62[url=http://iitjee2009solutions.targetiit.com]Solution Key with Question Paper of 2009 IIT JEE[/url]
1isn't d also correct?
F = -\frac{dU}{dr}
multiplying and div by dt , we get
F = -\frac{1}{v}\frac{dU}{dt}
since resultant of all forces is 0, v is also constant..
so, \frac{dU}{dt} = 0
that means potential energy does not change in time...
1i agree with shreyan.
potential energy of a system changes only when the configuration of the system changes. if resultant of all forces are zero then that means that these forces didnt produce any net change in the system's configuration.
so, d should also be correct.
62There are lots of mistakes in that solution key.. it was half cooked and not made well..
1i think the correct ans is D and i am bit sure of it.there might be some errors in the ans key.
