A worker is pushing a box of mass M up a rough incline by applying a horizontal pushing force of constant magnitude P. The incline makes an angle θ with respect to the vertical, and the coefficient of kinetic friction between the slope and the box is μ. Derive an expression for the acceleration of the box.

Which of the following situations is impossible? a) an object has velocity directed east and acceleration directed east. b) an object has zero velocity but non-zero acceleration. c) an object has constant non-zero velocity and changing acceleration. d) an object has velocity directed east and acceleration directed west. e) an object has constant non-zero acceleration and changing velocity.