Question

select the correct alternative.

• A. work done by kinetic friction on a body always results in a loss of its kinetic energy.
• B. Work done on a body, in the motion of that body over a closed loop is zero for every force in nature.
• C. Total mechanical energy of a system is always conserved no matter what type of internal and external forces on the body are present.
• D. When total work done by a conservative force on the system is positive then the potential energy associated with this force decreased.

Answer 1

The correct option is D When total work done by a conservative force on the system is positive then the potential energy associated with this force decreased.

$w=-△u$ (For conservative forces on the system)

$△u=-w$

If work done is $+ve$,

Then $△u=-ve$

$\therefore$ Potential energy decreases.