Under the circumstances of this case, the force inherently involved in the defendant’s penetration of the rape victim was sufficient to establish forcible rape. The victim had voluntarily engaged in other sexual activity with the defendant, but had made it clear that she did not wish to have intercourse and that defendant’s attempts to have intercourse with her were physically painful. The defendant nonetheless forced his penis into her vagina. Thus, even in the absence of evidence that the victim tried to pull away, or that the defendant used additional force to accomplish the act, the force used by defendant was sufficient for purposes of Penal Code section 261(a)(2).