The gas fills the right portion of a horizontal cylinder whose radius is 5 cm. the initial pressure of the gas is 1.01*10^5 Pa. a frictionless movable piston separates the gas from the left portion of the cylinder, which is evacuated and contains an ideal spring. the piston is initially held in place by a pin. the spring is initially unstrained, and the lenght of the gas-filled portion is 20 cm. when the pin is removed and the gas is allowd to expand, the lenght of the gas-filled chamber doubles. the initial and final temperatures are equal. determine the spring constant.