During that period of time, the bird's displacement was 4 km east. So its velocity was (4km east)/(11hrs). That's 0.36 km/hour east. (rounded)
The air inside becomes warmer, and that makes it LESS DENSE.
Less-dense air FLOATS in denser air. Since it's inside the balloon, it picks the balloon up when it floats.
Answer: KE = 25 J
Explanation: You must use the formula
KE = 1/2 m v²
to solve this problem.
KE = 1/2 (10 Kg) (5 m/s)
KE = 1/2 (50 kgm/s)
KE = 25 J
