A) In the case of the Boundary Thickness Layer we use the given formula,
We know as well that,
Re = Número de Reynolds =
Where,
U = velocity
= kinematic viscosity
For water, kinematic viscosity,
So,
B) For flat plate boundary layer. Given the Critical Reynolds Number.= 5*10^5 we know that is equal to Re above.
Thus,
C. Wall shear stress,
For water, dynamic viscosity, = 2.344*10^-5 lbf-s/ft^2
Answer:
C. At a particular instant
Explanation:
Speed is the defined as the ratio between the distance covered by an object and the time taken:
where d is the distance and t the time.
However, there are two possible measurements of speed:
- Average speed: this is the speed measured over a non-zero time interval (for example: a car moving 100 metres in 5 seconds; its average speed is
- Instantaneous speed: this is the speed of an object measured at a particular instant in time, so for a time interval that tends to zero. So, in the previous example, the average speed is 20 m/s but the instantaneous speed of the car at various instants of time can be different from that value.
To solve this problem we will apply the concepts related to the balance of forces. We will decompose the forces in the vertical and horizontal sense, and at the same time, we will perform summation of torques to eliminate some variables and obtain a system of equations that allow us to obtain the angle.
The forces in the vertical direction would be,
The forces in the horizontal direction would be,
The sum of Torques at equilibrium,
The maximum friction force would be equivalent to the coefficient of friction by the person, but at the same time to the expression previously found, therefore
Replacing,
Therefore the minimum angle that the person can reach is 46.9°
