When this pendulum swings, at which point is its kinetic energy the
highest? *

The bottom/center of the pendulum

Explanation:

As it swings, the pendulum will have maximum potential energy at the top of its arc.

As it comes back towards the center that potential energy will convert into kinetic energy until it reaches the middle of its swing (when the pendulum is fully vertical) where all potential energy has been converted into kinetic energy.

This is when the kinetic energy is the highest

As it begins to move away from the center of its arc, that kinetic energy will convert into potential energy again, and the process repeats

connect the batteries in series and hope

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