VITEEE 2016 Paper

Potential energy U for a system is defined as:
W‌int ‌=−∆U=−(Uf−Ui)...(1)

f

∫

i

→

F

⋅

→

dr

=−(Uf−Ui)...(2)
⇒ Where

→

F

is an internal conservative force, and W‌int ‌ is work done by the internal conservative force. ⇒ If U increases then Uf>Ui , or the term −(Uf−Ui) will be −ve .
⇒W‌int ‌ will become −ve
∴ System has done work against the conservative force