Question

Paragraph for Q. Nos. 21 to 26 Aball A is thrown up vertically with speed u. At the same instant another ball B is released from rest at a heighth vertically above the point of projection of A. Taking the moment of projection as t = 0 and acceleration due to gravity is 'g'. answer the following questions. 21. At any time instant t, the magnitude of relative acceleration of A with respect to B is (1) g (2) 29 (3) -29 (4) Zero 22. At any time instant t, the speed of A relative to Bis (1) u (2) u-2gt (3) Vu? - 2gh (4) u-gt 23. The separation between the bodies at any time instant t is (1) h (2) h- ut (3) h-ut + geriau (4) h- ut + gf

JEE/Engineering Exams

Physics

Solution

121

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P. Velocity of ball A in up direction ( =mathrm{Va}=mathrm{u}-mathrm{gt} ) Where, u = initial velocity ( mathrm{g}= ) acceleration due to gravity ( t= ) time Velocity of ball B in down direction ( =mathrm{Vb}=mathrm{gt}, ) (since initial velocity is zero) Therefore, velocity of ball A with respect to ball ( mathrm{B}=mathrm{u}-mathrm{gt}-mathrm{gt}=mathrm{u}-2 mathrm{gt} ) Therefore, velocity of ball A with respect to ball ( mathrm{B}=mathrm{u}-2 mathrm{gt} )