If the box is moving at constant velocity, net force must be zero, so:
F + fr = 0
fr = -F
<u>fr = -40 N</u>
 
        
                    
             
        
        
        
Answer:
Explanation:
Velocity of a wave is describe as 
velocity =Frequency × Wavelength
Mathematically 
v = fλ
Hence, Frequency, F = v / λ
Wavelength λ = v/f
So, if the frequency is kept constant, wavelength of the wave becomes directly proportional to velocity of the wave.
And this implies that, as the speed double, the wavelength is double.
 
        
             
        
        
        
Explain a police role, and how important it is. also you can explain a mayor's role and how important it is...
A police's role in the community is to protect us and make sure that everyone is following the rules. it is important for a police to be there so we can be safe. Their status is fair enough. Another Example is a mayor. a mayor's job is to improve the city/ the community. His status is high. There are many people around us that help us, each with a different status. 
**Tell me if you need more
        
             
        
        
        
Since the Earth is almost spherical in shape, we are actually to find first the volume of the spherical segment at a depth of 1,000 m. The radius of the Earth is 6,371,000 meters. The volume of a spherical segment is:
V = 1/3*πh²(3r - h)
Substituting the values and making sure the units is in mm,
V = 1/3*π(1000 m * 1000 mm/1 m)²[3(6,371,000 m * 1000 mm/1 m) - (1000 m * 1000 mm/1 m)]
V = 2×10²² mm³
Thus, the total amount of bacteria is:
2×10²² mm³ * 100 bacteria/1 mm³ = 2×10²⁴ bacteria