How long does it take for a package to fall from a hot-air balloon?

[suxatphysix]

Homework Statement

A hot-air balloon is ascending at the rate of 13 m/s and is 90 m above the ground when a package is dropped over the side.

(a) How long does the package take to reach the ground?


(b) With what speed does it hit the ground?

Homework Equations

The Attempt at a Solution

Tried 2a\Deltay=Vf^{2}-vi^{2}

I don't know if the initial velocity is 0 or 13m/s

 

[cristo]

If the balloon is ascending at 13m/s, then vi=13m/s (with the sign convention that upwards is positive). Try using the equation y=vi*t+0.5a*t^2.

 

[suxatphysix]

thanks, got part a right.

for b, I'm getting 42.18. is that right and would it be negative if it is going down?
used vf= vi + a*t and vf^2=vi^2+2*a*d

 

[cristo]

thanks, got part a right.

for b, I'm getting 42.18. is that right and would it be negative if it is going down?
used vf= vi + a*t and vf^2=vi^2+2*a*d

Yes and yes; although you only need to use the second equation.

 

[suxatphysix]

ty got it right