Spring Scale Calibrated with Known Weights

A spring scale, or newton meter, is a spring fixed at one end with a hook at the other. By Hooke's law the stretch grows in step with the force, so the marks on its scale are evenly spaced. This one is built in a clear tube with a paper scale and calibrated with known weights: on Earth a 100 g mass pulls with about 0.98 N (100 g × 9.81 m/s²). The sizes here are ours: a tube about 20 cm long and a light extension spring that stretches clearly under 1 kg. Do not load it past the heaviest calibration weight: an overstretched spring stays longer and the scale is lost.

مبتدئ

2 hours

التعليمات

Make the hooks

Bend two pieces of steel wire with round-nose pliers: one with a loop at each end to hang the spring from the top plug, one long rod with a loop at the top and a hook at the bottom.

المواد لهذه الخطوة:

سلك فولاذي0.4 m

الأدوات المطلوبة:

زرادية مستديرة الفك

Plug the tube

Push the top wire through one cork disc and glue the disc into the top of the tube. Make a hole in the second disc for the rod to slide through and glue it into the bottom.

المواد لهذه الخطوة:

أنبوب أكريليك (شفّاف)1 قطعة

قرص فلّين صغير2 قطع

غراء لحظي (سيانو أكريلات)1 قطعة

الأدوات المطلوبة:

سكين حِرَفية

Hang the spring

Hook the spring to the top loop and the rod's top loop to the spring, so the rod hangs out through the bottom plug. The lower end of the spring is the pointer.

المواد لهذه الخطوة:

نابض شد1 قطعة

Fit the scale

Glue a strip of graph paper along the outside of the tube and mark zero at the spring's lower end with nothing hanging.

المواد لهذه الخطوة:

ورق بياني1 قطعة

الأدوات المطلوبة:

قلم تعليم ثابت

Calibrate

Hang 100 g, 200 g and so on up to 1 kg, marking the pointer each time; each 100 g is about 0.98 N. The marks should be evenly spaced; check that the pointer returns to zero when unloaded.

الأدوات المطلوبة: