Question

Force acting on a particle is (2$\widehat{i}$ + 3$\widehat{j}$) N. Work done by this force is zero, when a particle is moved on the line 3y + kx = 5. Here value of k is –

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

Answer: (A)

2

Answer 2

Force is parallel to a line y = $\frac{3}{2}$ x + c

The equation of given line can be written as

y = $–\frac{k}{3}$ x + $\frac{5}{3}$

Work done will be zero, when force is perpendicular to the displacement i.e., the above two lines are perpendicular or

m₁m₂ = –1

or $\left( \frac{3}{2} \right)$ $\left( –\frac{k}{3} \right)$ = –1

or k = 2