# Physics

posted by on .

I found the first three parts of the question but I can't figure out part d.

The instruments attached to a weather balloon in the figure below have a mass(m) of 5.5 kg. The balloon is released and exerts an upward force(F) of 109 N on the instruments.

(a) What is the acceleration of the balloon and instruments?
10.02m/s^2

(b) After the balloon has accelerated for 10 s, the instruments are released. What is the velocity of the instruments at the moment of their release?
100.2 m/s

(c) What net force acts on the instruments after their release?
53.9N

(d) When does the direction of the instrument's velocity first become downward?
This is the one I can't figure out

• Physics - ,

direction of velocity is downward at maximum height, and net velocity is zero.

vf=0=vi+at=100.2m/s-g*t
solve for t. This time is seconds after the acceleration of 10s

• Physics - ,

I don't understand this formula?

• Physics - ,

these are the two answers I got...

10
or
10.22

• Physics - ,

how did you get the first three answers?