Science · Middle school

Spring balance

Hang masses on the hook, read how far the spring stretches and how many newtons it shows; compare three springs.

In the learning section below the figure, predict, try, complete the tasks and check yourself with short questions.

Fig. 1Spring balance

Drag a mass onto the hook, or use the buttons

0.00 N · 0.0 cm

Keyboard: ↓ hangs the next mass, ↑ takes the last one off, 1–3 pick the spring, Esc takes them all off.

Parts and inner mechanism

Apart0%

With the balance apart, hover over a part, tap it or pick it from the list; the arrow keys move through the list.

Pick a part to see what it does and why a real spring balance is made that way.

Masses

Spring

Your own values

Mass

1–1,000 g; a comma works as a decimal point too.

Spring constant

0.1–5 cm per N (k = 0.2–10 N/cm).

Balance reads

0.00 N

Mass: m = 0 g = 0 kg
Weight: F = m · g = 0 × 9.8 = 0.00 N
Stretch: x = 0.00 N × 2 cm/N = 0.00 cm
Stretch ÷ force: 2 cm/N

It stays the same whatever you hang: the stretch is directly proportional to the force. That is why the scale can turn the stretch straight into newtons.

Force–stretch graph

The dots are the loads you measured. They all lie on one straight line.

Change the spring: the ruler shows a different stretch, but the scale is drawn for that spring, so the force you read stays the same.

Learn

Progress is kept on this page only; no points are given.

1Predict
2Try
3Explain

With 200 g on the soft spring, the balance reads 1.96 N. If you swap in the stiff spring and hang the same 200 g, what will it read?

Weight is worked out as F = m · g (g = 9.8 N/kg, as in the lesson). While the spring stays within its elastic limit, it stretches by x = F ÷ k: the soft spring 2 cm per newton, the medium one 1 cm, the stiff one 0.5 cm. The weight of the hook and pull rod has been zeroed with the adjusting screw, so only the hung mass is measured. The pointer swings like a real spring and mass and settles with light damping; the damping is only for display. You can also type your own mass (1–1000 g) and spring constant (0.1–5 cm per N, that is k = 0.2–10 N/cm); the scale ends at 15 cm, so beyond that the pointer rests on the stop and the reading is off the scale.

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Spring balance

Parts and inner mechanism

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Your own values

Balance reads

Force–stretch graph

Learn

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