Answer:
 7revolutions
Explanation:
Given parameters: 
Initial revolution  = 250rpm 
Final revolution  = 150rpm 
Time  = 4.2s 
Unknown: 
Number of revolutions that occur at this time = ? 
Solution: 
To solve this problem; 
  let us find the change in revolution  = 250rpm - 150rpm  = 100rpm 
Convert the time to seconds; 
          60s makes 1 minute 
         4.2s will make  = 0.07min
   = 0.07min 
So; 
       The number of revolutions at this time  = 100rpm x 0.07min
          =   7revolutions
 
        
             
        
        
        
<span>Convert 200 km to meters which equals 200000 meters. Then take 10m/s*200000meters which equals 2000000 seconds.
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Potential energy does.
A book on the floor has negative potential energy relative to the seat 
of your chair, zero potential energy relative to the floor, and a whole 
bunch of positive potential energy relative to the ground if the floor 
is the floor of the passenger jet in which you are cruising and dropped 
your book on the floor.
        
             
        
        
        
Answer:
The greatest acceleration the man can give the airplane is 0.0059 m/s².
Explanation:
Given that,
Mass of man = 85 kg
Mass of airplane = 109000 kg
Distance = 9.08
Coefficient of static friction = 0.77
We need to calculate the greatest friction force
Using formula of friction

Where, m = mass of man
g = acceleration due to gravity
Put the value into the formula


We need to calculate the acceleration
Using formula of newton's second law


Put the value into the formula


Hence, The greatest acceleration the man can give the airplane is 0.0059 m/s².
 
        
             
        
        
        
Answer:
Option e. Blue/Violet
Explanation:
We know that when white light passes through a diffraction grating it spits into a band of seven colors or spectrum which includes the color in the order VIBGYOR that stands for Violet, Indigo, Blue, Green, Yellow, Orange and Red respectively.
Red light has the longest wavelength and is least scattered whereas Violet light with the shortest wavelength is the one to get most scattered and as we move far from bright spot at the center, there is an increase in the wavelength of light, thus the color that corresponds to the closest one is Violet with the shortest wavelength in the band.