The correct answer is:
<span>The rate at which a waves energy flows through a given unit of area
In fact, light intensity is defined as the light power per unit of area:
</span>

<span>but the power is the energy carried by the light per unit of time:
</span>

<span>this means that the intensity can be rewritten as
</span>

<span>
So, it's basically the rate of energy (per unit of time) through a given surface.</span>
Picosecond = 10 ^ -12 seconds.
Zeptosecond = 10^ -18 seconsds
Petaseonds = 10^15 seconds
To express Picoseconds into any of other two, you have to divide 10^-12 by the power index of the one in question
1Picosecond : 10^-12 / 10^-18 = 10^ (-12- 18) = 10^ (-12+18)= 10^6 zeptoseconds
1Picosecond : 10^-12 / 10^15 = 10^ (-12-15) = 10^-27 Petaseconds.
1Picosecond = 10^6 zeptoseconds
1Picosecond = 10^-27 Petaseconds
Echo sounding is a type of SONAR used to determine the depth of water by transmitting sound pulses into water. The time interval between emission and return of a pulse is recorded, which is used to determine the depth of water along with the speed of sound in water at the time.
I attached the missing picture.
The force of seat acting on the child is a reaction the force of child pressing down on the seat. This is the third Newton's law. The force of a child pressing down the seat and the force of the seat pushing up on the child are the same.
There two forces acting on the child. The first one is the gravitational force and the second one is centrifugal force. In this example, the force of gravity is always pulling down, but centrifugal force always acts away from the center of circular motion.
Part AFor point A we have:

In this case, the forces are aligned, centrifugal is pointing up and gravitational is pulling down.
Part BAt the point, B situation is a bit more complicated. In this case force of gravity and centrifugal force are not aligned. We have to look at y components of this forces, y-axis, in this case, is just pointing upward.
Part CThe child will stay in place at point A when centrifugal force and force of gravity are in balance:
It's most likely the combination of a bucket and the wheel.