Plain-English Meaning
When only conservative forces act, the sum of kinetic and potential energy never changes.
Mechanics questions usually become easier once you identify whether the problem is about force balance, kinematics, energy, or conservation.
Deeper Explanation
When only conservative forces act, the sum of kinetic and potential energy never changes.
Worked Example
Problem: A 2 kg ball is released from rest at h = 5 m. Find its speed just before hitting the ground.
- Set U_bottom = 0 (reference level).
- At top: K₀ = 0, U₀ = mgh = 2×9.8×5 = 98 J.
- At bottom: K = ½mv², U = 0.
- Conservation: 98 = ½(2)v² → v² = 98 → v ≈ 9.9 m/s.
Result: v ≈ 9.9 m/s
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At A Glance
Category: Mechanics
Levels covered:
Best use: Start with the formula meaning, then move to the worked example and quiz so the equation turns into a tool instead of a memorised line.