What is gravity? what is the difference between distance and contact forces?   what would be an example of each? describe two factors that are needed to calculate speed. hypothesize what might occur when a positive charged magnet is placed next to a negative charged magnet.   what might happen when a positive charge is placed next to a neutral charge? sally is trying to lift a heavy box, but is not strong enough to lift it.   would the force that she is applying to the box be an example of an unbalanced force or a balanced force?   why?