Sarah Attar, dressed in a white headscarf, green longsleeve shirt and black leggings, became the first Saudi woman to compete in Olympic track and field, finishing the 800 metres a half lap behind former world champion Janeth Jepkosgei. Former world champion Caster Semenya made her Olympic debut and advanced from an earlier heat in the 800, three years after being forced to undergo gender tests.
Semenya was sidelined for nearly a year while track and field's governing body decided whether to allow her to compete after she won the 2009 world title at age 18. After being cleared to return, she was runner-up at last year's world championships.
Again, a full house of 80,000 fans at the Olympic Stadium showed up for a morning session, and they reserved their wildest cheer for Somali-born Farah, who provided the climax to Super Saturday when he won the 10,000 in a magic three-gold, 44-minute spell for the host nation last weekend.
His rivals in the 5,000 didn't give him any extra space, as he had to fight for position several times before he put in a controlled dash for the line and a third-place finish which guaranteed him a place in Saturday's final.
"There was a lot of pushing and shoving trying to stay out of trouble," Farah said.
His training partner Galen Rupp, who took silver behind Farah in the 10,000, also qualified but only as fastest loser from the heats. Rupp's U.S. teammate Bernard Lagat also went through.
Pole vault qualifying was far less predictable, with world champion Pavel Wojciechowski failing to clear any height. Defending champion Steve Hooker of Australia bounced back from a disastrous start to the 2012 season to qualify for Friday's pole vault final along with European champion Renaud Lavillenie.
In the 800, Semenya of South Africa and defending champion Pamela Jelimo of Kenya also easily made it through to the semifinals but Ethiopia's Fantu Magisu, who won two Diamond League meets this year, did not start due to injury.
As expected world-record holder Ashton Eaton of the United States took control of the decathlon from the starting gun in the opening 100.
Eaton started off with an Olympic-best performance for a decathlete in the 100 (10.35 seconds) and followed it up by winning the long jump, too, with a leap of 8.03 metres.
After two events, Eaton led with 2,079 points, with fellow-American Trey Hardee in second place, 143 points behind. Former champion Roman Sebrle of the Czech Republic bowed out of the Olympics, retiring after one event with a heel injury.