a shopper in a supermarket pushes a cart with a q/c force of 35.0 n directed at an angle of 25.08 below the horizontal. the force is just sufficient to bal- ance various friction forces, so the cart moves at con- stant speed. (a) find the work done by the shopper on the cart as she moves down a 50.0-m-long aisle. (b) the shopper goes down the next aisle, pushing hor- izontally a