MediumPhysics
+4 / -1
-- Two spheres having masses 20 kg and 30 kg, moving in opposite directions with speeds of 15 m/s and 20 m/s respectively, strike each other and stick together. Kinetic energy of the composite body after collision will be
A
1275 J
B
8250 J
C
900 J
D
625 J
Explanation
Using conservation of momentum: m1v1 + m2v2 = (m1+m2)V. (20)(15) + (30)(-20) = (50)V => 300 - 600 = 50V => V = -6 m/s. Kinetic Energy = 1/2 * (m1+m2) * V^2 = 1/2 * 50 * (-6)^2 = 25 * 36 = 900 J. Note: Calculation check (300-600)/50 = -6. KE = 0.5 * 50 * 36 = 900 J. Correction: Let's re-read the options. Calculation: 1/2 * 50 * 36 = 900 J (Option 3).
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