Someone asked me this question today (this isn't homework, so don't worry): If a hammer and frying pan both having the same mass and same velocity hit a nail, which will drive the nail in farther? COR is assumed to be the same. Masses are the same, velocities are the same. Since everything is the same, I said it wouldn't matter as long as the nail is hit by the dead center of the hammer or frying pan. Is this correct?