Omega Mechanics

Classical Mechanics Level 5

A point source of light is rotating in a horizontal plane at a speed of $\omega$ rads/sec. There is a wall at a distance $d$ from the source. At some instant the focus of the light is at P and $\angle$ SPN = $\theta$ . Speed of the focus at this instant in terms of $\theta$ is :

\frac{\omega d}{\cos{\theta}}

\frac{\omega d}{\sin^2{\theta}}

\frac{\omega d}{\cos^2{\theta}}

\frac{\omega d}{\tan^2{\theta}}

\frac{\omega d}{\sin{\theta}}

\frac{\omega d}{\tan{\theta}}

1 solution

Rajdeep Dhingra
Feb 24, 2015

it will be better if you mentioned the point about which source is rotating.

Deepanshu Gupta - 6 years, 3 months ago

Could you edit it ? You are a moderator . Right ?

Rajdeep Dhingra - 6 years, 3 months ago

How? According to me, $$\frac{dx}{dt} = \frac{\del(d \cos{\theta})}{\del t} = d \frac{\del(\sin{\theta})} d \theta}{dt} = \boxed{\omega d \sin{\theta}}$$. Why is this wrong? How come $$\frac{\del \cos{\theta}}{del t} = \csc^2{\theta} \frac{d \theta}{dt}$$?

Kushal Thaman - 1 year, 11 months ago

Omega Mechanics

1 solution

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