Answer:
.
Explanation:
The efficiency of a machine is the ratio between the useful output and the energy input:
Rearrange this equation to find energy input in terms of efficiency and useful output:
.
Substitute in the values: 
and 
. Evaluate to find the value of 
:
.
(Rounded to two significant figures as in the value of efficiency.)
We can solve this problem using <span>Hagen–Poiseuille equation. Derivation of this equation is a bit complicated so I will just write down the equation.
</span>
This equation gives you the pressure drop <span>in an </span>incompressible<span> and </span>Newtonian<span> fluid in </span>laminar flow<span> flowing through a long cylindrical pipe of the constant cross section.
L is the length of the cylinder, Q is the volumetric flow rate, R is the radius of the pipe, and
is dynamic viscosity.
Dynamic viscosity of water at 20 Celsius is 0.001 PaS.
Now we can calculate the pressure drop:
</span>
<span>
</span>
Pushing pool tides something about the ocean
Answer:
Distance covered by B is 4 times distance covered by A
Explanation:
For an object in free fall starting from rest, the distance covered by the object in a time t is
where
s is the distance covered
g is the acceleration due to gravity
t is the time elapsed
In this problem:
- Object A falls through a distance 
during a time t, so the distance covered by object A is
- Object B falls through a distance 
during a time 2t, so the distance covered by object B is
So, the distance covered by object B is 4 times the distance covered by object A.
