Oil flows through a horizontal pipe of uniform cross-section. Between two points 1 km apart the pressure drops by 5 Pa. The density of the oil is 800 kg/m³. What is the change in kinetic energy per kilogram of oil between these two points?

6.25 * 10⁻³ J/kg
5.25 * 10⁻⁴ J/kg
3.25 * 10⁻⁵ J/kg
4.25 * 10⁻² J/kg

Correct answer: 6.25 * 10⁻³ J/kg

Solution

Bernoulli's equation per unit mass for a horizontal pipe links pressure change to kinetic energy change: the pressure energy per unit mass converted is delta P / rho. Dividing the pressure drop by the density gives the KE change per kg.

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