22: A 2.0 kg object moves along the x-axis under the influence of an unknown force. Its potential energy due to the force is U(x) = ax4 + bx2 , where a = 2.5 J/m4 and b = 12 J/m2 a) What is the force on the object when x = 0.5 m? b) If the object is released from rest at x = 0.5 m, what is its velocity when it crosses the origin?