The burner in a hot air balloon adds 6400 J of heat to the balloon while the ballon expands. As the balloon expands, it does 3100 J of work on the surrounding air. What is the internal change in thermal energy of the balloon?

the change in the internal energy of the balloon is 3,300 J

Explanation:

Given;

heat gained by the balloon system, Q = 6,400 J

work done on the surrounding air by the balloon, W = 3,100 J

The change in the internal energy of the system is calculated from the first law of thermodynamics;

ΔU = Q - W

where;

ΔU is the change in the internal energy of the balloon;

ΔU = 6,400 J - 3,100 J

ΔU = 3,300 J

Therefore, the change in the internal energy of the balloon is 3,300 J

does anyone know or what?

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.