A bird sitting on a hinged perch takes off from the perch, pushing the perch
in the opposite direction. The momentum of the perch

The momentum of the perch is equal to it's own momentum gather to take off

Explanation:

According to the Newton third law of motion which state that: in every action, there will be an equal and opposite reaction.

This is the law that helps us to walk, paddle boats e.t.c.

And momentum is always conserved. Therefore, the momentum of the perch is equal to it's own momentum gather to take off

explanation:

as the height from which the ruler was dropped increased, the speed of the ruler at ryan's hand increased.

i don't understand is there any other way you can rephrase it plz let me know in the comments and i will do it.

explanation: