Inception: why doesn't the van's motion 'kick' Arthur awake?

When explaining to Ariadne about kicks, Arthur's chair imbalancing is used as an example, right?Then when Arthur is dreaming inside the van dream, the van swerves and shifts enough to send Arthur flying down and around the corridors - why doesn't this act as a kick enough to wake him up?Before you say "because they were heavily sedated" - that's used to explain them not waking when killed in a dream, but not to prevent kicks waking them. Arthur does eventually get kicked awake by the van hitting the water, I'm just wondering why the motions of the van don't wake him before that. via /r/movies http://ift.tt/2tYpaDV