S3 Block and tackle · MVTTC Virtual Lab

Experiment workspace

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Tip: drag the green spring balance down to pull the rope. Press H for all controls.

Pull the effort rope0.00 m

Load mass

Friction in the pulleys

Big question: a machine lets a small effort lift a big load. What do we pay for this?

This pulley system has a velocity ratio VR = 4. The load weighs 100 N.

What will the spring balance read when we lift the load?

Why? (one short reason, optional)

How many rope parts hold up the lower block? Count them on the model first.

Pull the rope all the way. Read the spring balance, then record.

Spring balance

Effort moved

Load rose

0 readings

No.	Mass kg	Load N	Effort N	Effort dist. m	Load dist. m	MA	Eff. %
No readings yet.

Leave MA and efficiency empty. Work them out on your results sheet. Then change the friction and repeat.

MA = load ÷ effort. VR = effort distance ÷ load distance. Efficiency = MA ÷ VR × 100%.

Worked solution for the present set-up (7 steps)

The pulleys are oiled, so friction gets smaller. What happens to the efficiency?

The model is set up for you. Read the load and the spring balance, work out the efficiency, type it, then check. Three rounds.

Press Start to begin.

Score: 0 / 3

Runs offline. No trainee data is stored or sent. MVTTC · GST 04102 · S3 v2.1 · 3D model made in Blender · three.js (MIT licence).

Drag	the green spring balance down to pull the effort rope
Point at	a block, a rope or the load to see what it is
↓ ↑	pull or lower 2 cm at a time
P R	pull all the way; record a reading
1 2 3	camera: 3D, front, close-up
F M H	full view, sound on/off, this help