Three identical 6.4 kg masses are hung by three identical springs as shown. Each spring has a force constant of 7.8kN/m and is 12 cm long before any masses are attached to it. How long is the bottom-most spring going to be after three masses are hung on it? 14.3cm
16.2cm
12.8cm
10.7cm

The bottom-most spring going to be after three masses are hung on it is 14.3 cm

(a) is correct option

Explanation:

Given that,

Three identical mass = 6.4 kg

Force constant = 7.8 kN/m

Distance before attached mass = 12 cm

We know that,

When we attached three identical masses then the total mass on the spring will be 3 mg.

We need to find the extension

Using balance equation

For three masses,

Put the value into the formula

We need to calculate the length of the bottom spring

Using given length

Put the value into the formula

Hence, The bottom-most spring going to be after three masses are hung on it is 14.3 cm

(a) is correct option

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more

the bal will not change its velocity.