The Magpies had taken only two points from their previous six games while Bolton's victory over Blackburn in midweek ended a run of five straight defeats, and in the first half it appeared very much a battle between two struggling sides.
But the deadlock was broken in the 69th minute when Ben Arfa netted his first goal in more than a year and the prolific Ba doubled the lead soon after.West Brom 0 Man City 0Man Utd 5 Wigan 0Chelsea 1 Fulham 1Liverpool 1 Blackburn 1Stoke 0 Aston Villa 0Bolton 0 Newcastle 2Sunderland 1 Everton 1
Dimitar Berbatov smashed a hat-trick as Manchester United moved level with Manchester City at the top of the Barclays Premier League after a 5-0 win over 10-man Wigan while their rivals were held at West Brom.
Park Ji-sung gave the Red Devils an early lead when he converted after good work from full-back Patrice Evra.
The struggling visitors saw striker Conor Sammon shown a straight red card by referee Phil Dowd for raising his arm as he backed into Michael Carrick just before the break.
United soon made their advantage count as Berbatov (40) doubled the lead, with the Bulgarian netting again just before the hour.
Winger Antonio Valencia knocked in a fourth with 15 minutes left, before Berbatov completed his hat-trick from the penalty spot (77) after Antolin Alcaraz had fouled Park.
City, meanwhile, were left frustrated at The Hawthorns, where Mario Balotelli had an effort chalked off for offside after 33 minutes as the home side battled to a well-deserved point.
Chelsea's title hopes suffered another heavy blow as Fulham came from behind to consign them to a third successive 1-1 draw.
Fernando Torres flopped on his first league start for almost two months, although he did inadvertently lay on Juan Mata's 47th-minute opener, the winger's fifth goal of the season.
Fulham belied their miserable away record to equalise nine minutes later through Clint Dempsey's ninth of the campaign, ensuring the spoils were shared in the west London derby.
Bottom club Blackburn earned a 1-1 draw at Liverpool, where stand-in goalkeeper Mark Bunn produced an outstanding display.
Reds midfielder Charlie Adam put the ball into his own net on the stroke of half-time after a corner from Morten Gamst Pedersen to give Steve Kean's men a shock lead.
However, the home side rallied after the break, and were level through Maxi Rodriguez (53).
Despite plenty of pressure and the return of captain Steven Gerrard from a two-month absence with an ankle infection, Liverpool could not conjure a winner past inspired Rovers number two Bunn, who denied Andy Carroll again in stoppage time.
Sunderland had to be content with a point against Everton, who equalised with a controversial second-half penalty at the Stadium of Light.
The Black Cats looked on course to continue their revival under new boss Martin O'Neill when Jack Colback's 26th-minute effort deflected over keeper Tim Howard off Sylvain Distin to give the 22-year-old midfielder a first senior goal.
However, the visitors were back in the game when World Cup final referee Howard Webb pointed to the spot on 51 minutes after Leon Osman tumbled in the box despite there appearing no contact, Leighton Baines smashing home the resulting penalty.
In the evening game Stoke played out a dour 0-0 draw with Aston Villa.