Carbon 14 dating is a good method for dating a human leg bone rather than a dinosaur bone because, dinosaur bones date too far back for the shorter half life of carbon-14. Half-life is the time it takes for half of the radioactive nuclei to decay . And after about 6 half-life there is only about 1.56% left of the substance. It is harder to date anything beyond this given time because the dating is based off of the radioactivity of the subject.