Change in total energy of the system is equal to

Options

A. Work done by all the forces ( internal and external )
B. Work done by external forces .
C. Work done by internal conservative forces .
D. None of these

Answer

B

Explanation

Using work energy theorem we can write the following :
`W_(c ) +W_(ext) = K_(2) -K_(1)`
`rArr W_(ext) = (K_(2) -K_(1)) +(U_(2)-U_(1))= (K_(2)+U_(2))-(K_(1)+U_(1))`
`rArr " " W_(ext) = E_(2) - E_(1)`