The work done in pulling up a block of wood weighing 2 kN for a length of 10 m on a smooth plane inclined at an angle of \[{{15}^{o}}\] with the horizontal is :
A) 9.82 kJ
B) 8.91 kJ
C) 5.17 kJ
D) 4.36 kJ
Correct Answer:
C
Solution :
The various forces acting on a block kept on inclined plane are as shown. The force of resistance due to inclination when block is pulled upwards is \[F=w\sin \theta \] \[=mg\sin {{15}^{o}}\] \[=2\sin {{15}^{o}}\] = 0.5176 kN Also, work done = force x displacement \[=0.571\times 10=5.17\,kJ\]