MHT CET · Maths · Three Dimensional Geometry

If the lines given by \(\bar{r}=2 \hat{\imath}+\lambda(\hat{\imath}+2 \hat{\jmath}+m \hat{k})\) and \(\bar{r}=\hat{\imath}+\mu(2 \hat{\imath}+\hat{\jmath}+6 \hat{k})\) are
perpendicular, then the value of \(m\) is

A \(\frac{3}{2}\)
B \(\frac{-3}{2}\)
C \(\frac{2}{3}\)
D \(\frac{-2}{3}\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{-2}{3}\)

Step-by-step Solution

Detailed explanation

Given lines are \(\perp\) er and their d.r.s. are \((1,2, \mathrm{~m})\) and \((2,1,6)\)
\(\therefore \quad 1(2)+2(1)+m(6)=0\)
\(\therefore \quad 6 m=-4 \quad \Rightarrow m=\frac{-2}{3}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From MHT CET

Explore more questions on app

If the lines given by \(\bar{r}=2 \hat{\imath}+\lambda(\hat{\imath}+2 \hat{\jmath}+m \hat{k})\) and \(\bar{r}=\hat{\imath}+\mu(2 \hat{\imath}+\hat{\jmath}+6 \hat{k})\) areperpendicular, then the value of \(m\) is

Step-by-step Solution

If the lines given by \(\bar{r}=2 \hat{\imath}+\lambda(\hat{\imath}+2 \hat{\jmath}+m \hat{k})\) and \(\bar{r}=\hat{\imath}+\mu(2 \hat{\imath}+\hat{\jmath}+6 \hat{k})\) are
perpendicular, then the value of \(m\) is