An object is fired straight up with an initial velocity of 35.5 m/s. How long before the object hits the ground?

Answer 1

If your axis is pointing up, then your initial velocity vector is pointing up as well while acceleration vector is pointing downward.

The position equation for this object's motion is 0 (y _final) = 0 (y _initial) + v_it - gt²_/2.

After dropping zeros, cancelling by time, and multiplying both sides x 2,

you get 2v _i = gt or t = 2v_i/g. Now just plug in the numbers.