Force acting on a particle moving in a straight line varies with the velocity of the particle as F=k/v,where K is a constant.The work done by this force in time t is:
(A)K/v^2.t
(B)2Kt
(C)Kt
(D)2Kt/v^2
we are given
F = ma = K/v
or
m(dv/dt) = K/v
or
mvdv = Kdt
now integrating both sides
v varies form v1 to v2 while t from 0 to t, so
m(v22/2 - v12/2) = Kt
so,
(1/2)mv22/2 - (1/2)mv12 = Kt
thus,
change in KE = Kt
now, from work energy theorem
change in KE = work done
thus,
work done, W = Kt
correct answer is (c)