Recall the definitions of
• average velocity:
v[ave] = ∆x/∆t = (x[final] - x[initial])/t
Take the initial position to be the origin, so x[initial] = 0, and we simply write x[final] = s. So
v[ave] = s/t
• average acceleration:
a[ave] = ∆v/∆t = (v[final] - v[initial])/t
Assume acceleration is constant (a[ave] = a). Let v[initial] = u and v[final] = v, so that
a = (v - u)/t
Under constant acceleration, the average velocity is also given by
v[ave] = (v[final] + v[initial])/2 = (v + u)/2
Then
v[ave] = s/t = (v + u)/2 ⇒ s = (v + u) t/2
and
a = (v - u)/t ⇒ v = u + at
so that
s = ((u + at) + u) t/2
s = (2u + at) t/2
s = ut + 1/2 at²
The cat fell 1.0 m from the ground.
Using the formula
Here, 
Solving for t, the time it spent in the air is
The cat does not accelerate along the horizontal, so it has constant horizontal velocity. Since it strikes the floor 2.2 m from the table, then
For the same reason that you can skate around a curve at constant speed but not with constant velocity.
The DIRECTION you're going is part of your velocity, but it's not part of your speed.
If the DIRECTION changes, that's a change of velocity.
The object doesn't have to change speed to have a different velocity. A change of direction is enough to do it.
And any change of velocity is called acceleration.
"per second" is exactly the definition of "Hertz".
50 per second is 50 Hz. (B)
