A helium-filled balloon in the car will move to the left
Why?
Okay, so the car makes a left-hand turn. It experiences a centralizing pull to the left. Looking from the car's frame of reference, the balloon experiences a centrifugal force towards the right. Also, the air inside the vehicle experiences a centrifugal force towards the right.
Because of centrifugal force, both the air and the balloon trying to move to the right. But the wind has higher inertia than the balloon. So, air moves to the right of the aircraft and push the plane. Therefore a helium-filled balloon in the car will move to the left.
Hope this helps!
