Suvat question help

Question

A man is standing on a 29 metre building and throws a ball up in the air at 35 metres per second. The ball falls to ground at the base of the building – how long does it take to reach the ground?

Use acceleration due to gravity as -10 ms^-2 and write your answer to 3 decimal places. can someone help me solve this question

Answer 1

h(t) = at²/2 + v₀t + h₀

 

a = -10 m/s²

v₀ = 35 m/s

h₀ = 29 m

 

h(t) = -5t² + 35t + 29

 

Set h(t) = 0 and solve the quadratic equation for t.  It will give a negative and a positive solution.  The positive solution is correct.  You should get

 

t ≅ 7.749 sec

 

By the way, an almost identical problem was posted a few hours ago, and was answered correctly by 2 tutors.