"How can we turn garbage into energy?" Burn it.<p>"Why do cats purr?" Evolved basic social actions, display of affection/assuagement.<p>"Is it better to boil or bake?" Boil water, bake cake (or get bake).<p>"Can robots change their mind?" Only if they were programmed with algorithms that enabled them to.<p>"Why do some things bounce?" Newtonian laws of conservation of momentum, angular momentum and energy.<p>"Why do spinning balls curve?" The spin of the ball forces air around it in the direction of spin, coupled with a forward motion this produces a difference in air pressures on either side of the ball causing it to 'curve' a path through the air.<p>I can't help but feel the kids time would be better spent aiming their question at wikipedia instead of another thinly disguised Google Co. marketing site! ;)