Natural length of a spring is 60 cm and its spring constant is 4000 N/m. A mass of 20 kg is hung from it. The extension produced in the spring is (Take, `g = 9.8 m//s^(2)`)

Options

A. 4.9 cm
B. 0.49 cm
C. 9.4 cm
D. 0.94 cm

Answer

A

Explanation

Given, l = 60 cm = `60 xx 10^(-2)m`
m = 20 kg, k = 400 N/m
The weight hung from the spring
`= mg = 20 xx 9.8 = 196 N`
Suppose x is the extension produced in spring
Now, force applied by the spring = downward force on the spring
`therefore " "kx = mg implies x =(mg)/(k)`
`implies " "x = (20 xx9.8 )/(4000)=0.049 m = 4.9 cm`