Question:

The shortest distance between the skew lines $\bar{r}=(i+2\bar{j}+3\bar{k})+t(i+3\bar{j}+2\bar{k}) $ and $\bar{r}=(4i+5\bar{j}+6\bar{k})+t(2i+3\bar{j}+\bar{k})$ is

Updated On: Aug 15, 2022
  • $\sqrt6$
  • 3
  • $2\sqrt3$
  • $\sqrt3$
Hide Solution
collegedunia
Verified By Collegedunia

The Correct Option is D

Solution and Explanation

S.D = $\frac{\left[\overline{a} -\overline{c},\overline{b},\overline{d}\right]}{\left[\overline{b}\times\overline{d}\right]}$ $\bar{a} - \bar{c} = (\hat{i} + 2 \hat{j} + 3\hat{k} ) - ( 4 \hat{i} + 5\hat{j} + 6\hat{k})$ = $-3\hat{i} - 3\hat{j} -3 \hat{k} = -3(\hat{i} +\hat{j} +\hat{k} )$ $\bar{b} = \hat{i} + 3\hat{j} + \hat{k}$, $\bar{a} = 2\hat{i} +3\hat{j} +\hat{k} $ $\therefore$ $|\bar{a} \times \bar{b} | = \sqrt{9+9+9} = \sqrt{27} = 3 \sqrt{3}$ $\therefore$ S.D = $\frac{9}{3 \sqrt{3}} = \sqrt{3}$
Was this answer helpful?
0
0

Concepts Used:

Straight lines

A straight line is a line having the shortest distance between two points. 

A straight line can be represented as an equation in various forms,  as show in the image below:

 

The following are the many forms of the equation of the line that are presented in straight line-

1. Slope – Point Form

Assume P0(x0, y0) is a fixed point on a non-vertical line L with m as its slope. If P (x, y) is an arbitrary point on L, then the point (x, y) lies on the line with slope m through the fixed point (x0, y0) if and only if its coordinates fulfil the equation below.

y – y0 = m (x – x0)

2. Two – Point Form

Let's look at the line. L crosses between two places. P1(x1, y1) and P2(x2, y2)  are general points on L, while P (x, y) is a general point on L. As a result, the three points P1, P2, and P are collinear, and it becomes

The slope of P2P = The slope of P1P2 , i.e.

\(\frac{y-y_1}{x-x_1} = \frac{y_2-y_1}{x_2-x_1}\)

Hence, the equation becomes:

y - y1 =\( \frac{y_2-y_1}{x_2-x_1} (x-x1)\)

3. Slope-Intercept Form

Assume that a line L with slope m intersects the y-axis at a distance c from the origin, and that the distance c is referred to as the line L's y-intercept. As a result, the coordinates of the spot on the y-axis where the line intersects are (0, c). As a result, the slope of the line L is m, and it passes through a fixed point (0, c). The equation of the line L thus obtained from the slope – point form is given by

y – c =m( x - 0 )

As a result, the point (x, y) on the line with slope m and y-intercept c lies on the line, if and only if

y = m x +c