A steel wire of length 1.90 m with circular cross-section must stretch no more than 0.280 cm when a tensile (stretching) force of 420 N is applied to each end of the wire. What minimum diameter is required for the wire?

Express your answer in millimeters. Take Young's modulus for steel to be Y = 2.00 ×10^{11} Pa .

A1-lb collar is attached to a spring and slides without friction along a circular rod in a vertical plane. the spring has an undeformed length of 5 in. and a constant k =25 lb/ft. knowing that the collar is released from being held at a determine, the speed of the collar and the normal force between the collar and the rod as the collar passes through b.