Force

look at your teacher as he or she enters your class room.The teacher changes the positions .It this case the door,the blackboard,table,students are in the same place or position,but the teacher has changes the positions.Thus,the teacher is in motion.Some other examples are -a ball rolling on the ground,a bird flying,a dog running,all these show motion.Motion is the continuous change in position of a body with respect to bodies around it.You are traveling in a bus,the trees,houses, lamp posts,traffic signals remain where they are.They are said to be at rest.A body is said to be at rest when it does not change its position with respect to bodies around it.However,motion and rest are relative terms.It means that the same body may be at rest with respect to a certain body and in motion with  respect to another body.For example,when you are traveling in a bus,you are in motion with respect to trees,lamp posts,traffic signals etc.But you are at rest at the same time with respect to your fellow passengers as they see you stationary.