A block of mass 10 kg, moving in x-direction with a constant speed of `10ms^(-1)`, is subjected to a retarding force `F=0.1xxJ//m` during its travel from x=20 m to 30 m. Its final KE will beA. 475 JB. 450 JC. 275 JD. 250 J

A block of mass 10 kg, moving in x-direction with a constant speed of

1.	A block of mass 10 kg, moving in x-direction with a constant speed of `10ms^(-1)`, is subjected to a retarding force `F=0.1xxJ//m` during its travel from x=20 m to 30 m. Its final KE will beA. 475 JB. 450 JC. 275 JD. 250 J
Answer» Correct Answer - A From work-energy theorem, Work done = Change in KE `implies W=k_(f)-K_(i)` `implies K_(f)=W+K_(i)=int_(x_(1))^(x_(2)) Fx dx+1/2 mv^(2)` `=int_(20)^(20) -0.1.x dx+1/2 xx10xx10^(2)` `=-0.1 [x^(2)/2]_(20)^(30)+500` `=-0.005 [30^(2)-20^(2)]+500` `=-0.05 [900-400]+500` `implies K_(f)=-25+500=475 J`