An earth observer sees an alien ship pass overhead at 0.3c. The ion gun of the alien ship shoots ions straight ahead of the ship at a speed 0.4c relative to the ship. What is the speed of the ions relative to the earth observer?

The velocity of the ions relative to the earth observer is  

Explanation:

From the question  we are told that

     The speed of the alien ship is  

     The speed of the iron gun is  

The motion of the ions  relative to the earths observer can be mathematically represented as

substituting values

 =>  

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