A merry-go-round of radius R=2.0 m has a moment of inertia I=250 kg m2, and is rotating at 10 rpm. A child whose mass is 25 kg jumps onto the edge of the merry-go-round, by jumping directly toward the center at 6.0 m/s. The new angular speed (in rpm) of the merry-go-round is approximately A) 7.1 B) 8.5 C) 9.2 D) 10 E) 6.4 this is what i did: the moment of a thick disk is I = 1/2 MR^2... I THINK you could use that to find the mass of the merry-goat-round...but...if he jumps directly towards the center...does that have any impact on the rotational speed? I don't think it does. i would think the answer would be 10 but my friend got a different solution...is there anyway that someone can help telling what they got?