Problem 9 (4pm): A spring has a natural length of 10 cm. A 400 N force stretches the spring to 14- cm. a] Find the force constant, assuming the spring obeys Hooke's Law. b) How much work is done in stretching the spring from 10 cm to 14 cm? c] How far beyond its natural length could you stretch the spring if you doubled the work found in (13)? Problem 10 {4pm}: Find the ant-351W generated when the curve y = ln[1 + 2 x + x2) on the interval [0, 1] is revolved around the x-axis. Set up the integral and then use your calculator to approximate the arc length to 4 decimal places. Problem 11 [4pm]: A water tank that is half full of salt water has the shape ofan inverted cone with a height of6 m and a radius of 4 m [see gure). Assume the water is pumped out to the level that is 1 m above the top of the tank. The salt water has a density of1028 kg/ m3 and the acceleration clue to gravity is 9.8 m [52. 4m 6m