A spring loaded machine is able to launch a 2 kg disc 50 meters vertically into the air before it begins to descend. What was the initial velocity?

Velocity will be zero at top

Since both the initial velocity and time is unknown, the equation without time should be used,

     v² = v_o² + 2a_c(y - y_o)

Substituting the known values give,

     0 = v_o² + 2(-9.81 m/s²)(50 m)

     v_o = 31.32 m/s