The balloon without the coin is easy to move, but the balloon with the coin is not that easy to move and control.
Why is this? When you toss the balloon with the coin in the air you can’t tell which way it’s going to go. This is because the balloon center of gravity.
The center of Gravity is where the majority of and object weight is located. In the case of the empty balloon it’s leaning towards the mouth and with a ball its in the center.
Because the coin adds more weight to the balloon and doesn’t stay in one place the center of gravity is displaced. When gravity pulls an object down it acts on the center of gravity of that object. So if you know where the center of the object is you can tell where it’s going to go as it falls. Because the center of gravity is changing in the balloon with the coin and makes its hard to tell where it’s going to go.
When you are closer to the ground you have a lower center of gravity. Which is why race cars are so low. This helps them make tight turns and lessens the chance of flipping over.