Question

Three forces are acting on the block as shown in figure.


Find work done by net force if block moves $10\text{m}$ in horizontal direction. Given that $[F_1=20\text{N},F_2=5\sqrt{2}\text{N},F_3=10\text{N}]$

• A. $50\text{J}$
• B. $100\text{J}$
• C. $75\text{J}$
• D. $\text{No work done as friction is absent}$

Answer 1

The correct option is A $50\text{J}$

Let net force in horizontal direction be $F_{net}$
$\therefore F_{net}=F_1\cos {60}^{\circ }+F_3\cos {90}^{\circ }-F_2\cos {45}^{\circ }$
$F_{net}=20\times \frac{1}{2}+0-5\sqrt{2}\times \frac{1}{\sqrt{2}}=10-5=5\text{N}$


Displacement in horizontal direction $S=10\text{m}$
Work done by net force, $W$ $=F_{net}\times S$
$\Rightarrow W=5\times 10$
$\Rightarrow W=50\text{J}$