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JAMB Physics 1985 Question 13

Question 13

Elasticity

A force of 100 N stretches an elastic string to a total length of 20 cm. If an additional force of 100 N stretches the string 5 cm further, find the natural length of the string.

  1. A.15 cm
  2. B.12 cm
  3. C.10 cm
  4. D.8 cm
  5. E.5 cm
Show the answer and explanation

Answer: A (15 cm)

Explanation

The extra 100 N gives an extra 5 cm, so the first 100 N also stretched it 5 cm. Natural length = 20 − 5 = 15 cm.