If an object is projected upward with a velocity of 125 m/s...?

Question

What will be the total time elapsed until it reaches earth?
I also had to answer...
a)How high will it rise? I got 797.5M
b) How long until it reaches that height? I got 12.76s

For my 1st question, theoretically I could double "b". Anyone wanna verify?

Answer 1

Yes, to find the total time the object spends in the air you can double the amount of time it takes for the object to get to its highest point (assuming that it takes off and lands at the same altitude).
It takes the same amount of time for the object to go up as it does for it to come down. The object's speed as it hits the ground is the same as when it was initially launched, ignoring friction.

Answer 2

Velocity of projection u = 125 m/s
Total time i.e. time of flight = 2u/g
=2(125)/10
=250/10
=25 seconds

b) Time of ascent = u/g
=125/10
=12.5

a) Maximum height h = ut + 1/2 a t^2
h = ut - 1/2 g t^2
h = 125(12.5) - 1/2(10) (12.5)(12.5)
h = 1562.5 - 781.25
h = 781.25

Note: You'll get exact values if you consider g = 9.8, while i took it as 10 m/s^2

Answer 3

Yep, you got it right.