Answer:
A
Explanation:
Because of the convectional currents
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 energy that was lost due to air resistance while she was bouncing is determined as 3,360 J.
<h3>Conservation of energy</h3>
The amount of energy lost due to air resistance while she was bouncing is determined from the principle of conservation of energy.
ΔE = P.E - Ux
ΔE = mgh - ¹/₂kx²
ΔE = (50)(9.8)(16) - ¹/₂(35)(16)²
ΔE = 3,360 J
Thus, the energy that was lost due to air resistance while she was bouncing is determined as 3,360 J.
Learn more about energy here: brainly.com/question/13881533
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Answer: 20360 N
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