Work-Energy Theorem Examples in Physics
Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Work-Energy Theorem.
This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.
Concept Recap
The net work done on an object equals the change in its kinetic energy — the bridge between force and motion.
The total work done on an object is exactly what changes its kinetic energy.
Read the full concept explanation →How to Use These Examples
- Read the first worked example with the solution open so the structure is clear.
- Try the practice problems before revealing each solution.
- Use the related concepts and background knowledge badges if you feel stuck.
What to Focus On
Core idea: This theorem bridges force-based thinking (work) with energy-based thinking (kinetic energy).
Common stuck point: Only net work changes KE—individual forces may do positive or negative work.
Worked Examples
Example 1
easySolution
- 1 The work-energy theorem states: W_{\text{net}} = \Delta KE = \frac{1}{2}mv_f^2 - \frac{1}{2}mv_i^2.
- 2 Net work done: W = Fd = 20 \times 5 = 100 \text{ J}.
- 3 Since v_i = 0: 100 = \frac{1}{2}(4)v_f^2 \implies v_f = \sqrt{\frac{200}{4}} = \sqrt{50} \approx 7.07 \text{ m/s}
Answer
Example 2
mediumPractice Problems
Try these problems on your own first, then open the solution to compare your method.
Example 1
mediumExample 2
hardRelated Concepts
Background Knowledge
These ideas may be useful before you work through the harder examples.