Mistake Master

Potential Energy

Kinetic energy belongs to one moving object. Potential energy belongs to a system whose arrangement stores work waiting to happen. A ball above the ground; a compressed spring. Two formulas cover the course, $\Delta U_g = mg\,\Delta y$ near Earth and $U_s = \tfrac{1}{2}k(\Delta x)^2$ for a spring. The traps are small in number, and all of them come from forgetting that potential energy lives in the configuration, not the object.

A · SPRING SYSTEM F equilibrium Δx B · GRAVITY height y 5 m 4 m 3 m 2 m 1 m 0 m y2 y1 EARTH
The PELab sandbox at a glance. Left, a spring-block system compressed by $\Delta x = -0.55\ \mathrm{m}$ stores $U_s = 30.25\ \mathrm{J}$; the spring pushes the block outward with $F = 110\ \mathrm{N}$. Right, a ball-Earth system with the $U_g = 0$ reference dragged to $y_\text{ref} = 3.22\ \mathrm{m}$. The chosen zero changes $U_g$ at each height but leaves $\Delta U_g$ between heights fixed.
PELab · Open the sandbox and slide the zero-line →

Three traps. Treating potential energy as a property of the ball alone instead of the ball-Earth system. Doubling a spring's compression and expecting double the energy when the answer is four times as much. Calling a negative gravitational potential energy non-physical when it just reflects where the zero was chosen.

The work

3 ways in · any order
Lesson
Potential Energy

A five-section read covering gravitational and elastic potential energy, the system framing, and where the zero-point lives. Closes with a ten-scenario applet that drills the three pitfalls one at a time.

Skill check · 10 scenarios
Diagnostic
10-item topic check

Ten multiple-choice items targeting the three Topic 3.3 misconceptions, with two extra signed-energy items to catch sign-as-magnitude carryover.

Not started · 10 items · ~15 min
Targeted Practice
Drill a single misconception

Pick one of the failure modes you've missed and grind it on its own. The round is adaptive: two correct in a row clears the misconception and you move on.

Take the diagnostic to identify your misconceptions