<span> d = r*t is the basic distance equation
 d = 6000 km
 t with the tail wind = 6 hr
 r with the tail wind = speed of the plane + wind speed = s + w
 t with the head wind = 7.5 hr
 r with the head wind = speed of the plane - wind speed = s-w
 (s+w)*6 = 6000
 (s-w)*7.5 = 6000
 s + w = 1000
 s - w = 800
</span><span> 2s = 1800
 s = 900 km/h
 s + w = 1000
 w = 100
 Check the anwer by calculating the return trip.
 (900-100) * 7.5 = 800 * 7.5
 800 * 7.5 = 6000 km
 Answer: The rate of the jet in still air is 900 km/h. The rate of the wind is 100 km/hr.</span>
        
             
        
        
        
Answer:
21s
Explanation:
Given parameters;
Radius  = 10m 
Speed or velocity  = 3m/s 
Unknown: 
Period  = ? 
Solution: 
 To solve this problem, use the expression: 
       v  =  
  
r is the radius 
T is the unknown
            Input the parameters and solve for T; 
     3  =  
  
     62.84 = 3T 
          T  = 21s
 
        
             
        
        
        
The applicable equation:
P = F/A
P = pressure
F = Force or weight
A = surface area
Pressure on each cylinder = (W/n)/A
Where n = number of cylinders. Additionally, pressure in the reservoir is equivalent to the pressure in each cylinder.
Net pressure =  75 - 14.7 = 60.3 psi
Therefore,
60.3 = (W/n)/A = (450/n)/(πD^2/4) = (450/n)/(π*1.5^2/4) = (450/n)/(1.7671)
60.3*1.7671 = 450/n
106.03 = 450/n
n = 450/106.3 = 4.244 ≈ 5
The number of cylinders is 5.