Problem

A force

\mathbf{F} = -k(y\hat{i} + x\hat{j})

(where

k

is a positive constant) acts on a particle moving in the

x

y

plane. Starting from the origin, the particle is taken along the positive

x

-axis to the point

(a, 0)

and then parallel to the

y

-axis to the point

(a, a)

. The total work done by the force

\mathbf{F}

on the particle is (JEE 1998) a.

-2ka^2

2ka^2

-ka^2

ka^2