Answer:
because speed is the modulus of velocity which is a vector
the velocity to be zero it must be a round trip
Explanation:
This is because speed is the modulus of velocity which is a vector.
For the velocity to be zero it must be a round trip, therefore the resulting vector zero
On the other hand, the speed of the module is the same in both directions
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:
the total cross-sectional area of the capillaries is greater than the total cross-sectional area of the arteries or any other part of the circulatory system.
Explanation:
Blood velocity is not the same in all areas. In the capillaries it is where there is less speed, while in arteries and veins it is quite similar. This is due to the cross-sectional area of each of the vessels. It is a mistake to think of a vein, artery or capillary individually. We have to put them all together to see that the total area of the capillaries is 100 times larger than that of the arteries or veins. Blood flowing through arteries or veins is going faster because there is less area.
Blood velocity is inversely proportional to each of the areas of its territories. The greater the area, the lower the speed.
