Question

Three circular wires are attached in series such that, if one wire is rotated, other two also get rotated. If the diameter of a wire is $\frac{4}{5}$ times that of immediate left wire and the left most wire rotates at the speed of $32$ revolutions per minute, then the number of revolutions made by right most wire per minute will be

• A. $40$
• B. $49$
• C. $50$
• D. $60$

Answer 1

The correct option is C $50$

$1rev.\to \frac{1}{32}min$
$2\pi r\to \frac{1}{32}min$
$1\to \frac{1}{32\times 2\pi r}min$
$2\pi r^{\prime }\to \frac{1}{32\times 2\pi r}\times 2\pi r^{\prime }min\to \frac{1}{32\times 2\pi r}\times 2\pi \times \frac{16}{25}min$
$1rev.\to \frac{1}{50}min$
$1min\to 50revolution$