Question

A ladder ${}^{\prime }A{B}^{\prime }$ of weight $300N$ and length $5m$ is lying on a horizontal surface. Its centre of gravity is at a distance of $2m$ from end $A$. A weight of $80N$ is attached at end $B$. The work done in raising the ladder to the vertical position with end ${}^{\prime }{A}^{\prime }$ in contact with the ground is.

• A. $500J$
• B. $1000J$
• C. $1150J$
• D. $1900J$

Answer 1

The correct option is B $1000J$

Potential energy of the system is described by its amount of work done

$W=W_1+W_2$

$W=F_1{d}_1+F_2{d}_2$

$W=300\times 2+80\times 5$

$W=1000J$