Question

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. $89\,\,kJ$
• C. $4.35\,\,kJ$
• D. $5.17\,\,kJ$

Answer 1

Answer: (D)

$5.17\,\,kJ$

Answer 2

Here : weight of block $w=2 \,kN$, Distance $d=10\, m$ Angle of inclination on the plane $\alpha=15^{\circ}$ The block will be pulled up on a smooth plane Hence, force of resistance due to inclination $F =w \sin \alpha=2 \times 10^{3} \sin 15^{\circ}$ $=2 \times 10^{3} \times 0.2588$ $=0.5176 \,kN$ Now work done, $W =F d=0.5176 \times 10^{3} \times 10$ $=5: 17\, kN$