Task id16430

What should be the force F holding a block of mass m on a smooth inclined plane if the angle of inclination of the plane to the horizon is equal to a, and the force is directed along the plane (Fig.)? The coefficient of friction between the block and the plane is f. Neglect the friction between the block and the plane. Find the plane reaction force N and the traction force that must be applied to the block to lift it uniformly.