Answer:
<em>Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.</em>
Explanation:
<u>Potential and Kinetic Energy</u>
The gravitational potential energy is the energy an object has due to its height above the ground. The formula is

Where:
m = mass of the object
g = acceleration of gravity (9.8~m/s^2)
h = height
Note we can also use the object's weight W=mg into the formula:

The kinetic energy is the energy an object has due to its speed:

Where v is the object's speed.
Initially, the object has no kinetic energy because it's assumed at rest.
The W=30 N rock falls from a height of h=40 m, thus:

Since the sum of the kinetic and potential energies is constant:
U' + K' = 1,200 J
Here, U' and K' are the energies at any point of the motion. Since both must be the same:
U' = K' = 600 J
U'=Wh'=600
Solving for h':

Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.
The mass distribution along a particular axis affects the moment of inertia.
<h3>What is the moment of inertia?</h3>
Each component of the object's mass is now located at a different distance from the axis than it was previously if the axis is altered. Axes perpendicular to the rod that first travel through its center of mass and then through one of its ends are used to compare the moments of inertia of uniformly stiff rods.
As an illustration, you can easily change the direction of rotation by repeatedly wriggling a meter stick along an axis that passes through its center of mass. You will have a harder time moving the stick back and forth if you shift the axis to the end. Because a major portion of the stick's mass is located farther from the axis, the moment of inertia around the end is much larger.
To learn more about moment of inertia, refer to:
brainly.com/question/14460640
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Answer:
Value of magnitude of acceleration will be 
Explanation:
It is given that when a stone is dropped it takes 2.2 sec to reach the ground
(a) As the stone is dropped from the top of building
So its initial velocity
will be 0 m /sec
(b) As the stone is free falling and there is no external force applied on it so its acceleration will be equal to acceleration due to gravity
So value of magnitude of acceleration will be equal to
Answer:

Explanation:
The capacitance of the parallel-plate capacitor is given by

where
ϵ0 = 8.85x10-12 C2/N.m2 is the vacuum permittivity
k = 3.00 is the dielectric constant
is the area of the plates
d = 9.00 mm = 0.009 m is the separation between the plates
Substituting,

Now we can calculate the energy of the capacitor, given by:

where
C is the capacitance
V = 15.0 V is the potential difference
Substituting,

Answer:
-12.12
Explanation:
i just added them together and it worked.