Answer:
The Momentum Calculator uses the formula p=mv, or momentum (p) is equal to mass (m) times velocity (v). The calculator can use any two of the values to calculate the third.
Explanation:
There is a net force of 15N in The direction of Levi
Answer:
The Reynolds numbers for flow in the fire hose.
Explanation:
Given that,
Diameter = 6.40 cm
Rate of flow = 40.0 L/s
Pressure 
We need to calculate the Reynolds numbers for flow in the fire hose
Using formula of rate of flow


Where, Q = rate of flow
A = area of cross section
Put the value into the formula


We need to calculate the Reynolds number
Using formula of the Reynolds number

Where,
=viscosity of fluid
=density of fluid
Put the value into the formula


Hence, The Reynolds numbers for flow in the fire hose.
I don't personally know the answer, but this article should help!
http://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-a-black-hole-58.html