Wave is a disturbance or energy that propagate through medium from one point to other point
So basically it is a flowing energy that flows into the medium and hence medium particles start oscillating about their mean position to and fro.
This motion of medium particles or this to and fro motion is about their mean position and this will always be cyclic or periodic motion
This means the disturbance or energy continuously flow through the medium such that it will change the position of medium particle and this will be cyclic in order
For an example

so here above equation of wave is a travelling wave in which displacement of medium particle from its mean position is given by "y"
Now we can see that this disturbance depends upon the sine function and it will repeat its same position after every 2 pi time interval as it is cyclic function for this value
Due to this phenomenon of repeatation of its same position we can say that it is disturbance of wave is cyclic.
Power grid
All the poles and wires you see along the highway and in front of your house are called the electrical transmission and distribution system. Today, generating stations all across the country are connected to each other through the electrical system (sometimes called the "power grid").
As we know that when charge is released in electric field
It will have two forces on it
1. electrostatic force
2. gravitational force
now if the ball will accelerate upwards so we can say
net upward force = mass * acceleration


now we can find charge q on it by above equation

So above is the charge on the particle
Answer:
Ff = 19.6 N
Explanation:
So since its saying whats the minimum F to move the block, we will use static friction (0.5).
We will use the equation for force of friction, which is Ff = uFn
Ff = (0.5)(4)(9.8)
Ff = 19.6 N
this is the minumum force needed to move the block, as that is the frictional force. You would need to apply a minimum force of 19.6 N to move the block