Now let me give you an advice on how to win this dispute. You need to take with them on "devil's swing" spring scales, to put on a Cup of a weight, such as 1 kg, and keep track of the position of the pointer: it will show the same marked on weights weight, exactly one kilogram. This is proof immobility swing.
Indeed: if we together with a spring balance was describing circles about the axis, a weight, in addition to gravity, would also centrifugal effect, which in the lower part of the path would be the weight of the kettlebell, and the upper would reduce it; we have to notice that the weight becomes heavier, it weighs almost nothing. And if this is not observed, then rotates room, not us.
