Birds have hallow bones . explain how this is adaptive ? !

 This gives them the ability to fly. Solid bones would be to heavy for flight.

It is adaptive because it gives the birds The ability to fly

When the ball is rising up, it gains kinetic energy. when the ball reaches the very top, it will have all potential energy, until it falls back down and gains it kinetic energy. finally when you catch the ball or it falls back down, it would have gained its potential energy back.