An object is thrown vertically up with a speed of 15m/s. How much time passes before it comes down at 15m/s? (air resistance is negligible)
Vo = 15 m/s?.
V1 = 15 m/s.
Vf = Vo + g*Tr = 0 at max h.
15 - 9.8*Tr = 0.
Tr = 1.53 s. = Rise time.
Tf = Tr = 1.53s. = Fall time.
T = Tr+Tf = 1.53 + 1.53 = 3.06 s.