Question

Assertion- Frictional force is non conservative force Reason- frictional force depends on the path not on initial and final position of the object.

Using an example justify that the friction is a necessary evil give three advantages and disadvantages of friction mostly observed in our daily routine.

A body of mass 15g is pushed up on a rough inclined plane making an angle of 60° with a horizontal. The length of the inclined plane is 10m. The body goes up the inclined plane and comes to rest at the top of the inclined plane. From rest position, it again moves down. It is found that the time of ascent is half of the time of descent. Calculate a) The coefficient of friction between the body and the plane. b) The acceleration of the body when it moves up the plane. c) Time of descent. d) The acceleration of the body when it moves down the plane e) The force of friction between the body and the plane (take g=10 m/s²)