Physics
posted by applebottom .
A hotair balloon has a total mass of 720 kg. It accelerates downwards (towards the ground) at 2.7m/s^2 even though an upwards lift force in acting on it.
Find
a:Find the lift force acting on the balloon
B)What must be the total mass that needs to be thrown overboard if the operator on the hotair balloon decides to accelerate upwards at 3.6 m/s^2 ?
Assume the upwards lift force remains the same.

net force=ma
liftmg=ma but a=2.7
solve for lift. 
a. We'll call downward acceleration
(), and upward (+).
a + g = 2.7 m/s^2,
a  9.8 = 2.7,
a = 2.7 + 9.8 = 7.1 m/s^2.
F = ma = 720 kg * 7.1 m/s^2 = 5112 N.
b. a + g = 3.6 m/s^2,
a  9.8 = 3.6,
a = 3.6 + 9.8 = 13.4 m/s^2.
F = ma = 5112 N,
m * 13.4 = 5112,
m = 5112 / 13.4 = 381.5 kg, max.
m = 720  381.5 = 338.5 kg to be thrown overboard.