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A ball whose density is `0.4 xx 10^3 kg//m^3` falls into water from a height of 9 cm. To what depth does the ball sink ?A. 9 cmB. 6 cmC. 4.5 cmD. 2.25 cm |
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Answer» Correct Answer - B (b) The velocity of ball before entering the water surface `v = sqrt(2gh) = sqrt(2gxx9)` When ball enters into water, due to upthrust of water the velocity of ball decreases (or retarded) The retardation, a = `(apparent weight)/(mass of hall)` `(V(rho = simga)g)/(V rho) = ((rho = sigma)/(rho))g` `= ((0.4 - 1)/(0.4))xxg =- (3)/(2)g` If h be the depth upto which ball sink, then, `0 - v^2 = 2xx((-3)/(2)g)xxh` `rArr 2g xx 9 = 3gh :. h = 6 cm. |
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