i think its a or b

Which scenario describes periodic behavior?

A pendulum swinging back and forth

A ball bouncing up and down on the ground

The takeoff and landing of a jet plane

The path a dolphin swims in the ocean

3 answers

nvm i think i got this one
Both a and b are not truly periodic, since the oscillation gradually has lower and lower amplitude.

But, all other things being equal, I'd say the pendulum keeps its amplitude much better than the ball, so I'd have to go with (a)

Even (c), if the plane is always on time. <lol>
The answer is only : A pendulum swinging back and forth.
It cannot be the other options because when looking for a period behavior, we are also looking for something to come back to the initial starting point. Can't be the ball because logically it would eventually come to a stop. Can't be a plane because it is going from one location to another and will eventually stop. It can't be the dolphin because the dolphin will continue on swimming it the same direction and will not return to the initial start.