12,13,15,16,19,19,19,20,21,25 find the mean

17.9

Step-by-step explanation:

Add all of the numbers together.

You get 179

Divide by the amount of numbers, 10

you get 17.9

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(c) The potential energy of the object decreases while the kinetic energy increases.

Step-by-step explanation:

Given that, an object falls through Earth's atmosphere.

As there is no friction of drag, this is the case of free fall.

So, there is no restriction in the motion of the object due to the air molecule. i.e there is no rubbing of air molecule with the object, so there is no possibility of heat (thermal energy) generation. So, the thermal energy of the object remains constant. So, options (a) and (d) are incorrect.

The only force that acts on the body is the gravitational force, as there is no drag. This force causes only the acceleration of the body. The shape of the body remains unaffected. So, there is no strain in the body. Hence, the elastic energy of the body is zero and there is no change in it. Option (b) is also incorrect.

Now, due to gravitational force, the object falls towards the earth, and its velocity increases. As the object moves towards the center of the Earth, so, the distance between the center of the earth and the object is decreases, which leads to a decrease in the potential energy of the object (as the potential energy of any object due to another body is directly proportional to the distance between the center of both the body).

While, the velocity of the object increases, so the kinetic energy of the object increases (as the kinetic energy of any object of directly proportional to the square of the velocity of the object).

Hence, the potential energy of the object decreases while the kinetic energy increases.

Therefore, option (c) is correct.