Big question: when a load moves along a beam, how does its weight share between the two supports?
Make a prediction
Think first. Then the scales will be uncovered.
A 5 kg sandbag sits 0.25 m from support A on a 1.0 m beam (one quarter of the way along).
Which support carries more of the load?
Move. Observe. Compare.
Move the load and watch how the two readings change.
?Make your prediction first (step 1). Then the scales are uncovered.
Total:
Recorded readings
0 readings
Explain the readings
Take moments about support A. Each step is one small job.
Worked solution for the present set-up (7 steps)
Check yourself 1
The sandbag moves to the middle of the beam. What do the scales show?
Check yourself 2
A 10 kg load sits 0.2 m from support A on a 1.0 m beam. What does scale B read?
Beam challenge
Move the sandbag until scale B shows the target. Three rounds.
Score: 0 / 3
Big question: why are roof trusses and frames built from triangles?
Make a prediction
Both frames have pinned joints. We will push the top of each frame sideways.
Which frame will change shape?
Push and watch
Push both frames. Then add a brace and push again.
Press Push both frames.
Why triangles?
A square with pinned joints is a mechanism: the angles can change while every bar keeps its length.
A triangle can only change shape if a bar gets longer or shorter. Steel and timber bars hardly do that, so a triangle is rigid.
One diagonal brace cuts the square into two triangles, so it becomes rigid too. Roof trusses, bridges and pylons are made of triangles for this reason.
Check yourself
A gate frame is a rectangle. What is the best way to stop it sagging?
Rigid or not?
Each frame has pinned joints. Decide if it can change shape. Five frames.
Press Start to begin.
Score: 0 / 5