A force F→=3i^+4j^N is applied to a particle. The particle is displaced by 2m along the straight line ax-5y=8. If work done by the applied force is zero, the value of ‘a’ is

ax-5y = 8⇒y=a5x-85⇒m1=slope=a5Also slope of F→=3i^+4j^N is m2=43Since the work done is zero, applied force and displacement must be mutually perpendicular.∴m1 x m2=-1⇒a5 x 4 3=-1⇒a = -154