The rubber cord of a catapult has a cross-sectional area of 1 mm² and a total unstretched length of 10 cm. It is stretched to 12 cm and then released to project a stone of mass 5 g. Taking Young's modulus Y of rubber as 5 × 10⁸ N/m², the velocity of projection will be:
Correct answer: B. 20 m/s
- A. 20 cm/s
- B. 20 m/s
- C. 2 m/s
- D. None of these
Explanation
The potential energy stored in the stretched cord is E = (1/2)× Stress × Strain × Volume. This stored energy is convertedinto the stone's kinetic energy (1/2)mv². Solving this energybalance equation for velocity gives 20 m/s.
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Solids are compared through crystal structure, amorphous arrangement, elasticity, plastic deformation, stress, strain and Young’s modulus. Electrical behavior depends on available charge carriers and band structure, so conductors, insulators and semiconductors must be distinguished from mechanical properties such as strength, stiffness and brittleness.
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