Question

A force $\overrightarrow{10i}-\overrightarrow{5j}+\overrightarrow{7k}$ displaces a particle from the point $A$ to the point $B$. The position vectors of $A$ and $B$ are $\overrightarrow{3i}-\overrightarrow{j}+\overrightarrow{2k}$ and $\overrightarrow{i}+\overrightarrow{3j}+\overrightarrow{2k}$ respectively, then the work done is

• A. $40$
• B. $20$
• C. $60$
• D. None of these

Answer 1

The correct option is A $40$

Work done= $\overrightarrow{F}.\overrightarrow{D}$
The displacement vector in this case will be
$i+3j+2k-(3i-j+2k)$
$=-2i+4j$

Work done will be
$(10i-5j-7k)(-2i+4j)$
$=-20-20$ joules
$=-40J$

Magnitude of work done is $40$.