An object attached to a spring undergoes simple harmonic motion modeled by the differential equation m d 2 x d t 2 + k x = 0 where x ( t ) is the displacement of the mass (relative to equilibrium) at time t , m is the mass of the object, and k is the spring constant. A mass of 13 kilograms stretches the spring 0.9 meters. Use this information to find the spring constant. (Use g = 9.8 meters/second2) k = The previous mass is detached from the spring and a mass of 19 kilograms is attached. This mass is displaced 0.1 meters below equilibrium and then launched with an initial velocity of − 2 meters/second. Write the equation of motion in the form x ( t ) = c 1 cos ( ω t ) + c 2 sin ( ω t ) . Do not leave unknown constants in your equation. x ( t ) = Rewrite the equation of motion in the form x ( t ) = A sin ( ω t + ϕ ) . Do not leave unknown constants in your equation. x ( t ) =