[Q]: [Becauseithadbuiltonmovingsand.]
[A]: [Because it had built on moving sand.]
[Q]: [Heobtainedtheequationsofmotionfortheangularmomentumandforthecentreofmasswitharbitraryexternalforces.]
[A]: [He obtained the equations of motion for the angular momentum and for the centre of mass with arbitrary external forces.]
[Q]: [Thestabiliserhelpsyoubycompensatingforsmallmovementsofthehand]
[A]:
[The stabiliser helps you by compensating for small movements of the hand]