摩擦力练习题（Friction problem）.docVIP

摩擦力练习题（Friction problem） 13 Ask   friction condition is A  creates friction between object must meet the following three conditions: First, objects must be touched and stressed. Second, the interface is rough. Thirdly, there will be movement between the two objects in contact (with relative motion) or movement (relative position change). Ask  how judge two  static friction force between relative stationary objects A  can use the subjunctive. Assuming that there is no static friction force between two relative to a stationary object  if two objects will be changed from static to luck Dynamic  illustrate trend, where there is relative motion between two objects  namely static friction force between them  if two objects are static  explain it There is no relative movement between the trend of  that there is no static friction force. Such as objects on the  cant  will drop  without friction So still have a downward movement trend   by static friction force and the horizontal plane objects  without friction is not  movement There is no movement trend  hadnt been static friction force. Ask  friction has something to do with the object in the direction of the movement in the opposite direction?  A  in the analysis of the friction problem  must find out the effect of friction force is object relative motion  rather than hinder Dynamic  relative motion is a touch each other as reference object. The object movement may be as a reference to other objects Content. Therefore  friction is not always with the object in the direction of the movement in the opposite direction  sometimes with same direction  another object  friction is also are not necessarily resistance  sometimes can also be a dynamic  as people were walking foot back ground  if not skid  feet Relative to the ground has a tendency to - a backward movement  to feet make people have a forward friction  relative ground  into to move forward The motivation to move forward. Ask  inc