A stone of mass 20g is projected from a rubber catapult of length 0.1m and area of cross section 10?? m² stretched by an amount 0.04 m. The velocity of the projected stone is _______ m/s. (Young's modulus of rubber = 0.5 × 10? N/m²)
A stone of mass 20g is projected from a rubber catapult of length 0.1m and area of cross section 10?? m² stretched by an amount 0.04 m. The velocity of the projected stone is _______ m/s. (Young's modulus of rubber = 0.5 × 10? N/m²)
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1 Answer
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Loss in elastic potential energy = Gain in KE
½ (YA/L)x² = ½mv²
0.5 × (0.5×10? × 10? / 0.1) × (0.04)² = 20×10? ³ v²
0.5 × (5×10²) × 1.6×10? ³ = 20×10? ³ v²
0.4 = 20×10? ³ v²
v² = 20 => v = √20 ≈ 4.47 m/s
(Re-checking calculations)
0.5 * ( (0.5e9 * 1e-6) / 0.1) * (0.04)^2 = 0.5 * (5e2) * 1.6e-3 = 4.
0.5 * 20e-3 * v^2 = 10e-3 v^2
4 = 10e-3 v^2
v^2 = 400 => v = 20 m/s
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