M1 velocity acceleration Help

[Saucerer]

A balloon at a height of 300 m is descending at 10 m s- and decellerating at a rate of 0.4 m s-. How long will it take for the balloon to stop descending?
:eek:

[Unregistered]

hey well i didnt get ur ans right cuz if the balloon is fallin freely then deceleration has to be -9.8 m/s-2 i guess but however accordin to ur question u will use the equation v=u+at since it will stop desending when v=0 so if u use
v=0
u=10
a=.4
t=?

0=10+(.4)t

t=25 sec
hope u get it or its right

[Saucerer]

Got it sorted now thanx.

a should be -0.4 though surely.

v=0
u=10
a=-0.4
t=?

0=10+(-0.4)t

t=25 sec