question_answer

Which one of the following statements is correct?

i. Work and energy have different units.

ii. When an aeroplane takes off, the work done by its weight is positive.

iii. The potential energy of a spring increases     when it is extended and decreases when it is compressed

iv. When a body falls its kinetic energy remains constant.

v. When negative work is done by external forces on a system, the energy of the system decreases.

A) i, ii and iii

B) ii, iii and v             

C) Only v

D) iii, iv and v             

E) None of these