Answer:10 
Explanation:
You have to do speed divided by time so your answers 10 
 
        
             
        
        
        
Two major scientific discoveries provide strong support for the Big Bang theory: • Hubble's discovery in the 1920s of a relationship between a galaxy's distance from Earth and its speed; and • the discovery in the 1960s of cosmic microwave background radiation. Please give brainliest
        
                    
             
        
        
        
Answer:
The BOD concentration 50 km downstream when the velocity of the river is 15 km/day is 63.5 mg/L
Explanation:
Let the initial concentration of the BOD = C₀
Concentration of BOD at any time or point = C
dC/dt = - KC
∫ dC/C = -k ∫ dt
Integrating the left hand side from C₀ to C and the right hand side from 0 to t
In (C/C₀) = -kt + b (b = constant of integration)
At t = 0, C = C₀
In 1 = 0 + b
b = 0
In (C/C₀) = - kt
(C/C₀) = e⁻ᵏᵗ
C = C₀ e⁻ᵏᵗ
C₀ = 75 mg/L
k = 0.05 /day
C = 75 e⁻⁰•⁰⁵ᵗ
So, we need the BOD concentration 50 km downstream when the velocity of the river is 15 km/day
We calculate how many days it takes the river to reach 50 km downstream
Velocity = (displacement/time)
15 = 50/t
t = 50/15 = 3.3333 days
So, we need the C that corresponds to t = 3.3333 days
C = 75 e⁻⁰•⁰⁵ᵗ
0.05 t = 0.05 × 3.333 = 0.167
C = 75 e⁻⁰•¹⁶⁷
C = 63.5 mg/L
 
        
             
        
        
        
Answer: 91.94 kg
Explanation: Supoose Al's mass is m. The combined mass is 168kg, so Jo's mass is 168 - m.
The Law of Conservation of Momentum states that when two objects collide, the total momentum of both objects before the collision is the same as the total momentum of both objects after the collision.
At the beginning, Al and Jo are united without movement, so their initial momentum is zero. 
After the release of their hands, Al goes in one direction and Jo moves to the opposite direction. Suppose the direction Al is moving is positive. Conservation of momentum will be

where
index i referes to initial momentum
index f to final momentum
index 1 refers to Al
index 2 to Jo
Calculating:
![m(0.91)-[(168-m)(1.1)]=0](https://tex.z-dn.net/?f=m%280.91%29-%5B%28168-m%29%281.1%29%5D%3D0)


m = 91.94
Al has a mass of 91.94 kg.
 
        
             
        
        
        
Answer:
C. 2 and 4 
Explanation:
my teacher went over it and the answer was that