Answer:
Explanation:
Force between charge is given by the following expression
F = k Q₁ Q₂ / R² , k = 9 x 10⁹ , Q₁ and Q₂ are charges , R is distance between charges .
Putting the given values ,
.85 = 9 x 10⁹ x 7.1 x 10⁻⁶ x Q₂ / 5.4²
Q₂ = .85 x 5.4² / (9 x 10⁹ x 7.1 x 10⁻⁶ )
= .38788 x 10⁻³ C .
= 387.88 x 10⁻⁶ C .
6. D
7. D
8. B
let me know if you need clarification
Answer:L=109.16 m
Explanation:
Given
initial temperature 
Final Temperature 
mass flow rate of cold fluid 
Initial Geothermal water temperature 
Let final Temperature be T
mass flow rate of geothermal water 
diameter of inner wall 

specific heat of water 
balancing energy
Heat lost by hot fluid=heat gained by cold Fluid




As heat exchanger is counter flow therefore





heat lost or gain by Fluid is equal to heat transfer in the heat exchanger
(LMTD)




This is the upthrust on an object which is placed inside a fluid
This force act upwards and always push upwards
so the correct answer is given as
D. A force within a fluid that pushes upward
this force is always due to pressure difference at two levels of
at lower level since pressure is more that is why the force is upwards and this upthrust is known as Buoyancy