Answer:
about 4.097 seconds
Step-by-step explanation:
The vertical velocity is ...
(35 m/s)sin(35°) ≈ 20.075 m/s
When the projectile reaches the level from which it was launched (ground level), its final velocity will be the opposite of its initial velocity. Thus, the change in velocity is ...
-20.075 -(20.075) = -40.150 . . . . m/s
The acceleration is provided by gravity, which is -9.8 m/s², so the time required is ...
t = Δv/a = (-40.150 m/s)/(9.8 m/s²) ≈ 4.097 s
