The height of the bullet when the velocity is zero is 256 ft.
The height of the bullet when the velocity is zero is determined by taking derivative of the function as shown below;
[tex]v = \frac{dy}{dt} = 128 -32t \\\\when \ v \ is \ zero\\\\v = 0\\\\128 - 32t = 0\\\\32t = 128\\\\t = \frac{128}{32} \\\\t = 4 \ s[/tex]
The height of the bullet at this time is calculated as follows;
[tex]y(4) = 128(4) - 16(4)^2\\\\y(4) = 256 \ ft[/tex]
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