Explanation:
heat engine is correct answer 
 
        
                    
             
        
        
        
Answer:
If the two waves have the same amplitude and wavelength, then they alternate between ... In fact, the waves are in phase at any integer multiple of half of a period: ... The propagation velocity of the waves is 175 m/s.
Explanation:
please ask me in brainlist ok
 
        
             
        
        
        
Astronomers believe some stars are moving away from earth by measuring the extent to which their light is “stretched” into the red part of the color spectrum, representing the lower frequencies on that spectrum.
In short, stars moving away from earth are “red-shift”, while if they were moving towards the earth they would take on a “blue-shift”.
        
             
        
        
        
Explanation:
speed : • how fast an object changes position
 • miles per hour.
 • distance/time.
velocity: • speed in a direction
 • miles per hour North 
 • distance/ time in a direction