All posts by Engineer Manish Verma

IITian ~ Consultant & Educator manishverma.site

Cockroach on a Disc

A cockroach of mass m runs anticlockwise around the rim of a circular disc of radius R having moment of inertial I mounted on a frictionless vertical axis initially at rest. The speed of the cockroach with respect to the ground is v, whereas the disc turns clockwise with angular speed ω. The cockroach suddenly notices a bread crumb on the rim and, of course, stops immediately with respect to the disc. What is the angular speed of the disc after the cockroach stops?
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Speed of Light Symbol Short Quiz

Why does the symbol c usually represent speed of light in vacuum? Choose the best possible option.

(A) Einstein used the symbol c first time in his equation $\displaystyle E=m{{c}^{2}}$
(B) Einstein used the symbol c first time in his equation $\displaystyle m=\frac{{{m}_{0}}}{\sqrt{1-\frac{{{v}^{2}}}{{{c}^{2}}}}}$
(C) c is the initial letter of the word celeritas, the Latin word meaning speed
(D) c is the initial letter of the word calculus

Answer