[25 pts] The spring is compressed by a mass (m = 450 g) a distance of Ax - 9.0 cm. When the mass is released from rest, it travels along a frictionless track and stop at position A which is 30 cm above the ground. Take g - 9.80 m/s2. [Answer in 3 significant figures] A Ax r = 30 cm K B 1.2 m A. [10 pts] What is the spring constant k of the spring? B. [15 pts] If the track has friction, the mass now stop at position B where . What is the frictional force acting on the mass? [Hint: arc length , where 0 is in radian