Question

A brick weighing $4 - 0$ kg is dropped into a $1.0m$ deep river from a height of $2.0m$. Assuming that $80\%$ of the gravitational potential energy is finally converted into thermal energy, find this thermal energy in calorie.

Answer 1

To solve this question, we have to know about the potential energy, we know that, potential energy, stored energy that relies on the overall situation of different pieces of a framework. A spring has more potential energy when it is compacted or extended. A steel ball has more potential energy raised over the ground than it has subsequent to tumbling to Earth.

Complete step by step answer:
we have to find potential energy of the brick.
$P.E. = mgh$
Here, P.E is the potential energy. And m is equal to the mass of the brick, g is the gravitational force and h is the height. Now, after putting the values we get,
P.E = 4 \times 9.8 \times (2 + 1) \\\ \Rightarrow P.E = 4 \times 9.8 \times 3 \\\ \Rightarrow P.E = 117.6J \\\
According to the question, thermal energy is equal to $80\%$ of P.E.
Therefore the thermal energy is equal to
\dfrac{{80}}{{100}} \times 117.6 \\\ \Rightarrow 94.08J = 94.08 \times 0.239 \\\ \therefore 22.48512cal \\\
So, from this we can say, the thermal energy is $22.48512cal$.

Note: We can get confused between potential energy and kinetic energy. We know that kinetic energy, the type of energy that an article or a molecule has because of its movement. In the event that work, which moves energy, is done on an item by applying a net power, the article accelerates and in this manner acquires kinetic energy. We can say, Energy put away in an item because of its position is Potential Energy. Energy that a moving article has because of its movement is Kinetic Energy.