1.

A small sphere of radius 2 cm falls from rest in a viscous liquid. Heat is produced due to viscous force. The rate of production of heat when the sphere attains its terminal velocity is proportional to

Answer»

`2^2`
`2^3`
`2^4`
`2^5`

Solution :Rate of HEAT produced
`(DQ)/(DT) = F_v xx v_r". F_v = 6 pi eta R v_t`
`=6 pi eta r v_t xx v_t "" v_t = 2/9(r^2(rho - sigma))/(eta) g`
`(dQ)/(dT) prop r v_1^2 "" v_T prop r^2`
`(dQ)/(dt) prop r(r^2)^(2) IMPLIES (dQ)/(dT) prop r^5`
Here radius of the sphere is 2 cm, so `(dQ)/(dT) prop 2^5`.


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