It is an imaginary transformer which has no core loss, no ohmic resistance and no leakage flux. The ideal transformer has the following important characteristic. The resistance of their primary and secondary winding becomes zero. The core of the ideal transformer has infinite permeability.
The answer is C as there is more force on the left side ( excess of 5 N) which therefore pushed it to the right with a force of 5 N!
Answer:

Explanation:
The ball will rise decreasing its speed until it reaches the highest point where its speed will be zero. From this point the tennis ball will begin to fall again, in the free fall the tennis ball will gain speed but now in the opposite direction. When it returns to the same point where it was launched, its speed will be the same as the one that was launched but with the opposite sign.

We can check this using the equation:

where 
ang h is the height, but because the ball returns to the same point where it started, h =0
then


the initial and final velocity will be the same in number, but we know that the ball is going in the opposite direction, so the final velocity must have the opposite sign from the initial velocity
so if
,
