When empty, a particular helicopter of mass 3770 kg can accelerate straight upward at a maximum acceleration of 1.29 m/s2. A careless crewman overloads the helicopter so that it is just unable to lift off. What is the mass of the cargo?

Answer 1

Thrust= ma+mg= m(a+g) you are given a, mass, and g. solve for thrust.

Now, if cargo is added, so that a is zero.

Thrust=(masscargo+massplane)g
solve for masscargo

Answer 2

Fthrust - mg = m a
Fhrust = m (9.8+1.29)
do that to get Fthrust then

Fthrust - (m+mc)g = (m+mc)0 = 0
so
m + mc = Fthrust/g