Physics Force & Laws Of Motion Level: Misc Level

Sand from a stationary hopper falls on a mov-ing conveyor belt at the rate of 4.94 kg/s. The belt is supported by frictionless rollers and moves at 0.726 m/s un-der the action of a horizontal external force supplied by the motor that drives the belt.Find the frictional force exerted by the belt on the sand. Answer in units of N.