Question

Consider a river flowing toward a lake at an average velocity of 3 m/s. the river height is 90m above the lake. what is the total mechanical energy of the river water per unit mass in kj/kg?

Answer 1

Kinetic energy per unit of mass is

`K=(v^(2) )/(2)`

Given,
`v=3m/s^(2)`

Therefore,

`K=((3^(2) m/s^(2) )^2)/(2)`

`K=4.5 J/kg`

Now potential energy per unit mass is

`p=g* h`

Given,
`h=90 m`

Therefore,

`p= 9.8m/s^2 * 90`

`p=882.9 J/kg`

Thus, total mechanical energy of the river water per unit mass is

`T=K+p=(4.5+882.9)J/kg`

`T=887.9 J/kg`

OR

`T=0.887 kJ/kg`