4.5MechanicsStretch
Tilting
When a beam on two supports is about to tilt, it is on the point of rotating about one support — and the reaction at the other support becomes zero. This key idea unlocks tilting problems.
What you'll be able to do
- Recognise the condition for tilting
- Set a support reaction to zero
- Take moments about the pivot support
- Find limiting loads or positions
1
On the point of tilting
When a beam is about to tilt about a support, the reaction at the support is zero. Set that reaction to and take moments about the pivot support to find the limiting case.
The far reaction vanishes.
1On the point of tilting about B, the beam lifts off A.
2So .
Answer.
Tip — About to tilt about one support ⇒ the reaction at the OTHER support is zero.
Formula recap
Condition for tilting.
Take moments about the pivot.
Common mistakes to avoid
Setting the pivot support’s reaction to zero.
It is the OTHER (far) support whose reaction is zero.
Forgetting which support the beam tilts about.
Identify the pivot, then zero the far reaction.
Key takeaways
- On the point of tilting, the far support’s reaction is zero.
- Take moments about the pivot support.
- Use this to find limiting loads or positions.
Test yourself
Ready to lock in Tilting? Pick a mode and earn XP & Dobloons.