Question

A spiral spring of natural length 20.00cm has a scale

Answer 1

The  mass of the scale pan : 0.11 kg

Further explanation

Given

A spiral spring's length = 20 cm

mass 50 g ⇒ the length = 22 cm

mass 70 g ⇒ the length = 22.25 cm

Required

the  mass of the scale pan

Solution

Hooke's Law :

$\tt F=k.\Delta x$

The spring constant (k) :

$\tt k=\dfrac{\Delta F}{\Delta x}=\dfrac{g.(70-50)}{22.25-22}=\dfrac{g.20}{0.25}=g.80~g/cm=10~m/s^2\times 8~kg/m=80~N/m$

mass of the scale pan=m(for 50 g mass) :

$\tt (m+0.05).g=80\times (0.22-0.20)\\\\m=0.11~kg$