Question

On a particle, moving on a circular path with a constant speed $v$ , light is thrown from a projector placed at the centre of the circular path. The shadow of the particle is formed on the wall. The velocity of shadow, up the wall, is

• A. $\text{v } \text{sec}^{2 \, } \phi$
• B. $\text{v } \text{cos}^{2 \, } \phi$
• C. $\text{v } \text{cos } \phi$
• D. None of these

Answer 1

Answer: (A)

$\frac{\text{v}' \text{ cos } \phi}{\text{R } \text{sec } \phi} = \frac{\text{v}}{\text{R}}$
$\text{v}' = \text{v } \text{sec}^{2 \, } \phi$