Desc: Can You Really Knock Someone Out Harmlessly, Like in the Movies?: With Simon Whistler. Knocking someone out isn't as easy as in the movies. Physically hitting someone requires multiple blows or a very precise blow with just the right amount of force to fall between being ineffectual and causing death. Basically the 'dosage' of the blow has to be just right which is also true of knock out, injected and orally administered drugs. And drugs can take quite some time to take effect.