Angular Momentum and Angular Impulse
A spinning wheel has angular momentum $L = I\omega$. A torque acting over time delivers angular impulse $J = \tau\,\Delta t$, the signed area under a $\tau$-vs-$t$ graph. One rule links them: $J_{\text{net}} = \Delta L$. The trap is the wrong graph; the area under $\tau$-vs-$\theta$ is rotational work, not impulse.
Three traps. Reading area under any $\tau$-graph as impulse, when only $\tau$-vs-$t$ does ($\tau$-vs-$\theta$ area is rotational work). Treating a torque value as an impulse value, when impulse needs the duration too. Calling the angular momentum of a straight-line particle zero, when $L = mvd$ about any chosen axis, with $d$ the perpendicular distance from the axis to the line.
The work
3 ways in · any order
Lesson
Angular Momentum and Angular Impulse
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The rule $J = \tau\,\Delta t = \Delta L$, the rotational version of linear impulse. Read the signed area under a $\tau$-vs-$t$ graph, then drill the rule on a ten-scenario applet.
Diagnostic
10-item topic check
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Ten items hitting the three main traps: reading the wrong area, mistaking torque for impulse, and missing the angular momentum of a straight-line particle. About fifteen minutes.
Targeted Practice
Drill a single misconception
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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.