A tow truck weighing 6000 lb attempts to jerk a wrecked vehicle back onto the roadway using a 15-ft length of steel cable 1 in. in diameter (E = 12 x 106 psi for the cable). The truck acquires a speed of 3 mph at the instant the cable slack is taken up, but the wrecked car does not move.
(a) Estimate the impact force applied to the wrecked vehicle and the stress produced in the cable.
(b) The cable breaks in the middle, and the two 7.5-ft halves are connected in parallel for a second try. Estimate the impact force and cable stress produced if the wrecked vehicle still remains fixed.