Question

With mass of 20g hung from its end the total length of a spring is 12cm.When the mass is increased to 32g,the total length of the spring is 14.4cm.What is the unstretched length of the spring

Answer 1

Answer:

Unstretched length = 8cm

Explanation:

Let,

Unstretched length be L

In the equation of spring force,

Spring force = kx

x is the length that is stretched

Therefore in the given case,

Spring force = Weight of the body

kx = 20g

k(12 - L) = 20g   ---------(1)

Spring force = Weight of body

kx = 32g

k(14.4 - L) = 32g   ---------(2)

(1) / (2) =>

(12 - L) / (14.4 - L) = 20g/32g

32(12 - L) = 20(14.4 - L)

384 - 32L = 288 - 20L

384 - 288 = 32L - 20L

12L = 96

L = 8

Hence,

Unstretched length = 8cm