A mass is attached to a spring with an unknown spring constant. The spring gains 10 J of elastic potential energy if stretched by 10 cm. How far would the spring need to be stretched to give the spring 20 J of elastic potential energy? Use proportional reasoning.

Option 1: 14 cm
Option 2: 28cm
Option 3: 20 cm
Option 4: 40 cm

From the given information in the question, the correct option is Option 1: 14 cm.

A non-stretched elastic spring has a conserved potential energy which gives it the ability to perform work. The elastic potential energy can be expressed as:

PE = k

Where PE is the energy, k is the spring constant and x is extension.

i. Given that: PE = 10 J and x = 10 cm, then;

PE = k

10 = k

20 = 100k

k = 0.2 J/cm

ii. To determine how far the spring is needed to be stretched, given that PE = 20 J.

PE = k

20 = (0.2)

40 = 0.2

= 200

x =

  = 14.1421

x = 14.14 cm

So that;

x is approximately 14.00 cm.

Thus, the spring need to be stretched to 14.00 cm to give the spring 20 J of elastic potential energy.

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