Asmall block with mass 0.0400 kg is moving in the xy-plane. the net force on the block is described by the potential-energy function u(x, y) = (5.80 j/m2 ) x2 − (3.60 j/m3 ) y3 . what are the magnitude and direction of the acceleration of the block when it is at the point (x=0.300 m, y=0.600 m)? draw the acceleration vector with components, and make a sketch of the potential energy vs. x and y