Question

Two rods A and B of the same material and length have their radii $r_1$ and $r_2$ respectively. When they are rigidly fixed at one end and twisted by the same couple applied at the other end, the ratio of the angle of twist at the end of A and the angle of twist at the end of B is

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

$\tau =\frac{\pi n{r}^4}{21}\theta$
In the given problem, $r^4\theta =$ constant
Therefore $\frac{{\theta }_A}{{\theta }_B}=\frac{r_2^4}{r_1^4}$