Question

why does the frictional force on a body decrease as soon as it is accelerated?

Answer 1

The key point here is not the acceleration of the body but a comparison of the frictional force on a moving body compared with the same body while stationary. Even if a body is moving with constant velocity (zero acceleration) the frictional force will be less than that of the body while stationary. Anyways, the reason the body at rest experiences a greater frictional force is due to several effects that increase the adhesion between the body and the surface. Prolonged contact between two surfaces produces a gradual plastic deformation ("creep") of the microscopic protuberances of the surfaces, permitting the surfaces to mate more closely, with more intimate contact. Furthermore, atoms migrate from one surface into the other, and the surfaces actually grow into each other. Finally, the films of contaminants covering the surfaces tend to split apart when subjected to a steady tangential push, such as the lateral push supported by the surfaces before "breakaway"; and gaps in the films then permit stronger adhesion between the bare materials. All of these effects contribute to greater adhesion between the stationary body and the surface than occurs when there is relative motion between them. Hope this helps!

Answer 2

thank you very much!!

Answer 3

It's simple, as body is accelerated then the force F=ma increase dat will overcome frictional force, dats y we push the object by giving jerks ( acceleration) rather than to push it uniformly (constant velocity)over the rough surface