Answer:
Because there's buoyancy force
Explanation:
What is wrong here is that he assumes that gravity is the only force affecting the weight of the balloon on the scale here. In reality there's also buoyancy force which lifts the full blown balloon upwards.
A better type of container would be an air tank where its volume does not change when it's empty and when it's full of air.
We could determine the acceleration using this formula

Given from the question v₀ = 23 m/s, v₁ = 0 (the car stops), t = 5 s
plug in the numbers



a = -4.6
The acceleration is -4.6 m/s²
Yes, an object<span> that was set in motion in the past by some force, but that is no longer being acted on by a net force, is </span>moving<span> but with </span>zero acceleration<span>, i.e. it is </span>moving<span> at constant velocity.</span>