Calculating Acceleration with Force and Mass

[saychanh]

Homework Statement

The instruments attached to a weather balloon in the figure below have a mass(m) of 4.8 kg. The balloon is released and exerts an upward force(F) of 109 N on the instruments. What is the acceleration of the balloon and instruments?

Homework Equations

F = ma

The Attempt at a Solution

F = ma
109N = (4.8 kg)(a)
a = 109N / 4.8kg
a = 22.7 m/s^2

I got this answer, but its not the right answer.

 

[G01]

Remember that it is the sum of the forces that equals ma. You have not added up all the forces. There is one very important force that you have forgot about. What else is pulling on the system?

 

[saychanh]

oh right, i got it. thank you