Posted by **Lindsay** on Wednesday, November 28, 2007 at 3:21pm.

A research balloon of total mass 200 kg is descending vertically with a downward acceleration of 3.2 m/s^2. How much ballast must be thrown from the car to give the balloon an upward acceleration equal to 2.8 m/s^2, presuming that the upward lift of the balloon does not change?

Could someone at least show me the first steps? I don't even know where to begin.

- Physics -
**bobpursley**, Wednesday, November 28, 2007 at 3:31pm
The upward lift is constant, it depends only on the size of the balloon.

netforce= mass*acceleration

Lift-mg=m*a

lift-g(m-deltam)=(m-deltam)*newacc

1)solve for lift in the original equation, knowing m, a, and g.

2) solve for deltamass in the second equation knowing lift, g, m, and the new acceleration.

- Physics -
**Lindsay**, Wednesday, November 28, 2007 at 4:01pm
For lift I got 1320, and for deltamass I got 304.76. Is this right? If so, do I have to add those to the netforce?

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