If you pull on a door handle, the door opens. If you sit on a bed, the springs in the mattress compress and, ＿＿（36）＿＿ of the compression, exert an upward force on you. We know from experiences that some sort of force is ＿＿（37）＿＿ to do these jobs. There are two basic classes of forces, ＿＿（38）＿＿ whether the agent touches the object or not. Contact forces are forces that act on an object by touching it at a point of contact. The majority of forces are contact forces. Long-range forces are forces that act on an object ＿＿（39）＿＿ physical contact. Magnetism is an example of a long-range force. You have undoubtedly held a magnet ＿＿（40）＿＿ a paper clip and seen the paper clip leap up to the magnet. A coffee cup released from your hand is pulled to the earth by the long-range force of gravity.