An experiment that produces waves on a string is analyzed, and the experimental value for the wave speed is found to be 66 m/s.
2 answers:
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A) 
b)
c)
b)
c)
Answer B is the correct answer
We know that kinetic energy , where m is the mass of object and v is the velocity of object.
In this case only velocity is the variable, mass remains constant.
So point having higher velocity has higher kinetic energy.
When it leaves the racket, the ball will be having a certain height, but just before it reaches the ground it will not having any height. So maximum velocity of ball is at that time when it reaches just above the ground.
So option B is the correct answer.