A block of mass 412 g is pushed against the spring (located on the left-hand side of the track) and compresses the spring a distance of 4.6 cm from its equilibrium postiion. The block starts from rest, is accelerated by the compressed spring, and slides across a frictionless horizontal track. It leaves the track horizontally, flies through the air, and subsequently strikes the ground. The acceleration of gravity is 9.81 m/s^2. What is the spring constant? answer in units of N/m.