Why there is friction between the two object?

Answer 1

Friction does NOT vary depending upon whether an object is pushed or pulled. The frictional force (static or dynamic) is proportional to the normal force, the force that counteracts and exactly matches the weight of an object that is at rest (or moving at constant velocity). The frictional force will oppose the direction of the force applied to an object to move it. It matters not whether the object is pulled (using a tensile force) or pushed (using a compressive force). Besides F = ma, another good concept to always keep in mind when discussing motion problems is this: the sum of the forces on an object moving at constant velocity is zero. An object that is at rest has a constant velocity of zero; hence, the sum of the forces acting upon it must be zero. If you place a book on a level desktop, for example, the book will just sit there. The force due to gravity (i.e., weight) is matched perfectly by a force -- the normal force -- equal and opposite in direction. The sum of all the forces on the book, therefore, is zero. If you apply to the book a force parallel to the desktop, the book will move (once the force of static friction as been overcome). When it moves, its velocity is no longer zero, so there was a change in its velocity. We can therefore conclude that the book accelerated, however briefly. During the brief period that the book accelerated, we know that the sum of the forces acting on the book was non-zero. The force you applied to the book to get it moving was sufficient to overcome the frictional force that resisted your efforts to move the book. When the book's velocity reaches a constant value, the sum of the forces acting on the book is again zero. When the book starts to slow down, the sum of the forces is non-zero, and when the book comes to rest again, the sum of the forces acting on it is, once again, zero. A THOUGHT: If you push or pull exactly horizontal then the friction force should be the same. In practice however, you often push at a downward angle. Only part of your applied force is horizontal. The other part is vertically down. This adds to the object's weight and the Normal force increases and then so will friction, as it is proportional to the normal force. When you pull, you frequently pull at an upward angle. The vertical part of your applied force is up which subtracts from the object's weight, resulting in a smaller Normal force and a smaller frictional force.

Answer 2

it is easier to push because pulling starins your musles when you push you can push with any part of your body and when you pull you usally have to pull with your hands

Answer 3

Friction releases thermal energy and reduces speed and efficiency.

Answer 4

Its because of the irregularities in both the surfaces. The irregularities oppose each other in opposite direction. The opposition is called friction.

Answer 5

Push