If you fall on your femur and it hurt (maybe a lot), will it break if it was the same fall that hurt your femur, on a weaker bone? Please be specific?

Possibly. In theory, since the femur is thick and strong, it can withstand more force than smaller, "weaker" bones; however, there's really no way to predict if a certain fall would have resulted in a broken bone since there are many other factors to consider. .