Work Energy Theorem: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Work Energy Theorem. Understanding the underlying formula is key to arriving at the correct answer below:

Apply conservation of energy with non-conservative forces: initial energy $E_i = \frac{1}{2}mv^2 = 200\text{ J}$. Final potential energy at $18\text{ m}$ is $U_f = mgh = 180\text{ J}$. Energy lost against air friction is $\Delta E = E_i - U_f = 200 - 180 = 20\text{ J}$.