Helicopter Physics: Solving the Time of Release Problem

[mekias4]

A helicopter's window is 5 ft above its skids. The helicopter starts on the ground and lifts straight into the air at a constant speed of 2 mph. A passenger in the helicopter drops an object from the window and the object hits the ground at 25 mph. How long did the passenger wait after lift off before releasing the object?

I am not sure what formulas to use for this problem and and do I want to figure out time final or time initial. Please help explain this to me.

 

[JaredJames]

I'd look at this with an equation of motion:

Convert 2mph and 25mph to SI units.

Using v = u + at
where v = final speed, u = initial speed, a = acceleration due to gravity.

From there you can calculate t.

Note: Remember to get your signs right or your answer will be wrong, u will not be 0 to begin.