what do you mean by frictionless distal
Answers
Answer:
If no forces are acting upon the skater and he is on a frictionless surface, then that means he has no net acceleration. ... If an object moves with a velocity and there is no acceleration, then the velocity remains constant.
Answer:
Friction
When two objects in contact are forced to move on each other, the resistant force that occurs at the contact surface opposite the direction of movement is friction. Friction that exists before one of the objects starts to move is called static frictional force. Static friction is the amount of force necessary to start movement of an object in a static state. Kinetic friction (or dynamic friction) is the friction that exists during the movement of the object, and it is the amount of force that the object must overcome to continue moving. A typical friction graph is shown in Fig 4-1. Static friction is proportional to the force; as the force increases, the friction also increases. When the force comes to a critical point (f max), the static friction is overridden and the object starts to move. From this point on, resistance to movement of the object is called kinetic friction. Theoretically, kinetic friction has lower values than static friction.
Friction between solid objects can be rolling or sliding, depending on the type of movement. Because orthodontic tooth movement is a slow process, the wire and bracket relationship can exhibit both static and kinetic forms of sliding friction because the application of force starts a complex biomechanical relationship between the wire-bracket-ligature-tooth-periodontium system and the alveolar bone. Before we give this relationship any detailed consideration, it is necessary to understand friction.
When a book on a table is in a stable state, it applies a load or force (A) equal to its weight on the table (Fig 4-2a). The table conducts a force (N) on the book of the same magnitude and in the opposite direction. Force A is the result of many force vectors spread over the entire surface of the book; if the book is of a homogenous structure, these force vectors will spread out equally on the contact surface, so the resultant vector of these forces is located in the geometric center of the book. The same conditions are valid for the resultant force N.
If the book is pushed lightly from left to right (Fig 4-2b), because of the force acting on the book (P), the magnitude, direction, and point of application of the force N begin to change, and so does the book’s homogenous distribution. The cause of this is the roughness of the contact surface. Let’s assume for a moment that the contact surface is a frictionless and vacuumed environment. In this case, after starting movement with a minor force (P), the book would maintain its velocity and direction in accordance with Newton’s first law, and no changes in the magnitude, direction, or point of application of the N force would occur. However, in this example, there is a rough, interlocking contact surface between the table and the book that could be seen if examined under a microscope. When the book is pushed with horizontal force P, it does not start to move immediately because of the resistant force (ie, friction) resulting from the interaction between these two materials. This resistance (frictional force [f]) is equal to and opposite force P, creating a resultant force (R).