Different speeds of light through two separate media ... and the difference in wavelength caused by the difference ... causes the bending of waves fronts associated with light rays.
AFTER the bend, since the light rays then travel in a different direction, we may also say that the 'velocity' has changed.
Answer:
3.31m/s
Explanation:
Angular momentum for 3s is



Moment if inertia is


Angular speed
ω = L/I

The speed of each ball is
V = ωL

A hypothesis is an educated guess. It's your own opinion!
Between 1589-1592 when he discovered projecctile motion