Bernoulli's equation incorporates a sign convention where upward movement and forces are considered positive, while downward movement and forces are negative. This convention is crucial for maintaining consistency in calculations involving gravitational potential energy (GPE), which is defined as the negative work done by gravity. As an object ascends, its GPE increases, and conversely, it decreases when descending. The potential energy term in Bernoulli's equation is expressed as density multiplied by gravitational acceleration and height, adhering to this established sign convention.
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shanewatson said:In Bernoulli's equation, why the work on fluid at the lower end of the pipe is taken as negative?
please explain why the force is negative to displacement at the lower end?
The convention is to consider upwards movment and upwards forces as positive, and downwards movement and downwards forces as negative. Gravitational potential energy is the negative of the work done by gravity, so GPE increases (more positive or less negative) as an object moves upwards, and decreases as an object moves downwards. The potential term in Bernoulli's equation follows the same rule, but it's potential energy per unit volume (density x gravitational acceleration x height).shanewatson said:please explain why the force is negative to displacement at the lower end?