Sehwag played a ball onto his stumps from James Pattinson shortly before tea.
The pair had stood only a few centimetres from each other and exchanged angry words in the seventh over of the innings.
Pattinson's arm had gone close to Sehwag's elbow as the batsman ran to the non-striker's end to score a single.
Sehwag brushed shoulders with paceman Peter Siddle in the 15th over and the batsman immediately raised his hand in apology which was accepted by Siddle.
Sehwag reached his half-century with a straight-driven four off spinner Nathan Lyon and repeated the dose next ball before another booming drive almost carried to long-on from the last delivery of the over.
Dropped on 11 by Mike Hussey at gully off Pattinson's bowling, Sehwag had another life on 58 when wicketkeeper Brad Haddin dived in front of first slip and only succeeded in throwing his wrist at the ball.
Ben Hilfenhaus had taken the new ball for Australia and struck in his fourth over when Gautam Gambhir was caught behind for three.
Australia's tail wagged as the home side were bowled out for 333 after resuming on 6-277.
Australia lost Haddin (27) and Siddle (41), both to left-arm quick Zaheer Khan (4-77). They had shared an important partnership of 72 for the seventh wicket.
The highlight of day one for Australia was a 113-run partnership between debutant opener Ed Cowan (68) and ex-skipper Ricky Ponting (62) for the third wicket.
Australia's 13th man Dan Christian was a substitute fielder for Cowan who was resting because of a sore back.
- AAP
