Limit word problem- helicopter jump

[Aoiro]

Hi, I need help with this question

At a publicity event, Ayida, a stuntperson, will jump out of a helicopter with a jetpack on her back. The jetpack allows her to achieve a net upward acceleration of 4.4m/s^2 for a single interval of maximun length 10s. Ayida wants to time the use of the jetpack so that she lands with a zero velocity.
a) If the helicpter is 100m height, when should Ayida turn on her jetpack? When will she land?
b) If the helicopter is 200m height, when should Ayadia turn on her jetpack? when will she land?
c) What is the maximum height from which Ayida can jump to land with zero velocity?

I don't know where to start can someone explain this problem thanks.

 

[courtrigrad]

Use the equation y = y_{0} +v_{y0}t + \frac{1}{2}a_{y}t^{2}. You can differentiate this to get v_{y} = v_{y0}+a_{y}t

 

[Aoiro]

How did you get that equation?

 

[radou]

How did you get that equation?

It's a 'standard' equation of displacement for motion with constant acceleration.