A block of mass  10 kg , moving in  x  direction with a constant  speed of 10 ms-1, is subjected to a retarding force  F = 0.1 x J/m during its travel from  x = 20 m to  30 m. Its final KE will be

Here, m=10 kg,vi=10 m s-1Initial kinetic energy of the block is Ki=12mvi2=12×(10 kg)×10 m s-12=500 Jwork done by retarding forceW=∫x1x2Frdx=∫2030-0.1xdx=-0.1x222030=-0.1900-4002=-25 JAccording to work energy theorem,W=Kf-KiKf=W+Ki=-25 J+500 J=475 J