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Two springs of force constants 300 N/m (Spring A) and 400 N/m (Spring B) are joined together in series. The combination is compressed by 8.75 cm. The ratio of energy stored in A and B is (E_A)/(E_B). The (E_A)/(E_B) is equal to

Asked in JEE Main Online 2013 · Spring combinations and force constants

• (1) 4/3
• (2) (16)/9
• (3) 3/4
• (4) 9/(16)

Step-by-step solution

Why the other options are wrong

• (2) Comes from squaring the ratio of spring constants; the energy at equal force goes as 1/k, not 1/k².
• (3) Comes from taking the energy proportional to k; that holds at equal compression, not at equal force.
• (4) Comes from squaring and inverting.

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