Calculate work done to move a body of mass 10 kg along an incline $(\theta=30^{\circ})$ with constant velocity through a distance 10 m $(g=10 m/s^2)$

$(a)\;1000 \;J \quad (b)\;500 \;J\quad (c)\;250\;J \quad (d)\;10\; J$

Sir,but the total force on body will be zero and even the velocity is constant. So how could be work done a\c work enegy theorem?

We need to apply an external force, $F=mg \sin \theta$ up the plane, while the body is in motion downwards.
$\Rightarrow W = F\;d = mg \sin \theta \; d$
Given $d=10\;m, m = 10 Kg, \theta = 30^\circ, g = 10 m/s^2$,
$W=10 \times 10 \times \sin 30 \times 10$
$\quad=100 \times \large\frac{1}{2}$$\times 10$
$\quad=500\;J$
edited Aug 25, 2014