Acceleration is the change in velocity
It'll be 152 Hz at the exact instant the bumblebee
is right at the tip of your nose, on his way past you.
Before he gets there, while he's coming at you,
he sounds like a frequency higher than 152 Hz.
After he passes by, and is going away from you,
he sounds like a frequency lower than 152 Hz.
the weight of the balloon is .030 * 10 = 0.3 N
the weight of the gas of volume v is 0.54*10 N
The lifting force of a volume of v m³ of displaced air is 1.29v N
so, we need
1.29*10*v = 0.3 + 0.54*10*v
or
1.29v = 0.03+0.54v
