in Aikido, Aite (the true term for the partner, not Uke) goes along the movement mostly to protect himself, for example, if Aite tries to resist when Juji Garami Nage (crossed arm projection) is used against him, he risks having both arms broken.
Also Aikido isn't based on jujustu but on Daito ryu aikijujutsu and it's used on the tournament because Taiho-justu (used by the policewoman) have strong Aikido bases, mostly because on 1947 when he was created Aikido, as a pacifist art, was the only martial art permitted by the Allied occupation forces