Two wheels, each marked with a dot on its rim, are mounted side by side. Initially the dots are alinged and wheels are at rest. One of the wheels is given a constant angular acceleration of `(pi//2) rad//sec^(2)` and the other wheel is given a constant angular acceleration `(pi//4)rad//sec^(2)`. Both acceleration are in the same direction. Find the time (in s) after which the two dots will becomes alingned again for the first time.

Answer

4

Explanation

Dots will be aligned again after time `t`, if the slower disc makes on rotation less than other disc.
`2pin(1/2)(pi/2)t^2`……….i
and `2pi (n-1)=(1/2)(pi/4)t^2`……….ii
By dividing `n/((n-1))=2/1` or `n=2`
From eqn i `t=4s`.