QUICK REVIEW
Quick Review — Static Equilibrium and Stability — Algebra-Based
Refresh the essential ideas and relationships for Static Equilibrium and Stability in just a few minutes.
TIME
5–10 minutes
BEST FOR
A rapid refresh
FINISH WITH
Key ideas refreshed
After this quick review, you'll be able to...
recall the essential ideas and decide what to review next.
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Course Alignment
This Physics Sensei Unit Review is an independent learning resource. Use it to reinforce key concepts, prepare for homework, or review before a quiz or exam.
RESOURCE: Physics Sensei Unit Review | UNIT ID: MEC-U23 | TOPIC: Static Equilibrium and Stability | COURSE LEVEL: Algebra-Based
BEST USED ✓ After learning the unit ✓ Before starting homework ✓ Before a quiz or exam
Your Review Plan
Complete these four stages to quickly refresh the essential ideas and confirm you're ready to continue.
4 Stages • Approximately 5–10 minutes.
Quick Recall
Let's quickly refresh what you already know. These short recall activities will help you bring the most important ideas back to mind before reviewing them.
QUICK RECALL
Recall Activity
Complete the three statements from memory before revealing the answer.
Write the three key relationships: net horizontal force, net vertical force, and net torque for static equilibrium. Then write the magnitude of torque produced by a force F applied a distance r from the pivot at angle θ.
Reveal Answers
ΣFx = 0, ΣFy = 0, Στ = 0, and τ = rF sin θ.
Why it works: Zero net force prevents translational acceleration; zero net torque prevents angular acceleration.
Ready to refresh the essentials?
Great! Now let's review the most important ideas you'll want to remember.
Essential Idea
Take one last look at the most important concept from this unit. If you remember this idea, the rest will come back much more easily.
ESSENTIAL IDEA
Static Equilibrium Means ΣF = 0 and Στ = 0
For a rigid body to remain at rest, the vector sum of all external forces must be zero and the sum of all external torques about any chosen origin must be zero. Torque magnitude is τ = rF sin θ. Choosing a convenient pivot can eliminate unknown forces from the torque equation.
ΣFx = 0, ΣFy = 0, Στ = 0, and τ = rF sin θ.
Example: For a horizontal beam supported at one point, take torques about the support so the unknown support force produces zero torque.
Sensei note: Do not use rF unless the force is perpendicular to the lever arm. Use rF sin θ when needed.
Ready to check your memory?
You've refreshed the essential idea. Now see how much you remember before moving on. Need a quick reminder?
Confidence Check
You've refreshed the essential ideas. Now answer this quick confidence check to confirm you're ready to move on.
CONFIDENCE CHECK
Support Force and Torque
Answer all three without notes.
A 4.0 m uniform beam of weight 200 N is hinged at its left end and held horizontal by an upward cable force at the right end. What cable force is required if the cable force is vertical?
Reveal Answers
Take torques about the hinge: T(4.0 m) − (200 N)(2.0 m) = 0, so T = 100 N.
Why it works: The beam weight acts at its center, 2.0 m from the hinge. The hinge forces give no torque about the hinge.
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Next Step
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