A copper wire of length l and radius r is nickel plated till its final radius is 2r. If the resistivity of the copper and nickel are `rho_(c)` and `rho_(n)`, then find the equivalent resistance of the wire.

Answer

`2 m//s`

Explanation

Velocity of lighter block at the instatn the string just gets taut `v = sqrt(2gh) = sqrt(2 xx 10 xx 1.8) = 6 m//s`
Now by impulse `-` momentum theorem, let common speed be `v_(1)` then `(2 + 1) v_(1) = (1) v rArr v_(1) = (v)/(3) = (6)/(3) = 2 m//s`