What is the velocity of a wave that has a wavelength of 6 m and a frequency of 3 hz?

The unit Hz is the same as 1/s

v = λ x f = (6 m) x (3 Hz) = (6 m) x (3 1/s) = 18 m/s

18 m/s

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.