Bernoulli's Principle density and velocity

[physgrl]

Homework Statement

The density of the liquid flowing through a horizontal pipe is 1600 kg/m3. The speed of the fluid at point A is 4 m/s while at point B it is 8.0 m/s. What is the difference in pressure, PB - PA, between points B and A?



a. -1.9 x 10^3Pa

b. -3.8 x 10^4Pa

c. +4.5 x 10^4Pa

d. +5.0 x 10^4Pa

*e. -7.7 x 10^4Pa

Homework Equations

Pa+1/2*ρ*va²=Pb+1/2*ρ*vb²

The Attempt at a Solution

Pb-Pa=1/2*ρ*va²-1/2*ρ*vb²
Pb-Pa=1/2*ρ*(va²-vb²)
Pb-Pa=1/2*1600kg/m³*(4m/s²-8m/s²)
Pb-Pa=-3.84x10⁴Pa

and the answer key says its -7.7 x 10^4Pa
what did I do wrong? :s

 

[LawrenceC]

The answer in the book is incorrect. You have the correct answer.

 

[physgrl]

Thanks :)