M/s, km/h, and mph are all used to measure these quantities
        
                    
             
        
        
        
      The force that prevents motion when the surfaces of two objects come into contact is known as friction. Friction decreases a machine's mechanical advantage, or, to put it another way, reduces the output to input ratio.
<h3>How can I figure out the frictional force?</h3>
         The resistive force of friction (Fr) divided by the normal or perpendicular force (N) pushing the objects together yields the coefficient of friction (fr), which is a numerical value.
 The formula fr = Fr/N serves as a representation of it.
Therefore, 100N of force is needed to move an item with a mass of 50 kg.
It will accelerate by 10 m/s2.
If a substance's mass does not change over time, friction cannot affect it. Instead, friction can be affected in a variety of ways by an object's mass.
To  Learn more About Friction, Refer:
brainly.com/question/24338873
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<h2>
Time taken is 0.459 seconds</h2>
Explanation:
We have equation of motion v = u + at
      Initial velocity, u = 0 m/s
      Final velocity, v = 81 km/hr = 22.5 m/s    
      Time, t = ?
      Acceleration, a = 49 m/s²
      Substituting
                       v = u + at  
                       22.5 = 0 + 49 x t
                       t = 0.459 seconds
    Time taken is 0.459 seconds
 
        
             
        
        
        
Answer:
The trains mass in pounds would be 40084.029 if you would round it to the hundreths 
Explanation:
 
        
                    
             
        
        
        
Its option 3 an object has potential energy