[" With what velocity should a particle be projected so "],[" that its height becomes equal to radius of earth? "],[[" (1) "((GM)/(R))^(1/2)," (2) "((8GM)/(R))^(1/2)],[" (3) "((2GM)/(D))^(1/2)," (4) "((4GM)/(D))^(1/2)]]