Two equal masses travel towards each other on a frictionless air track at speeds of 60 cms-1 and 30cms-1. They stick together on impact.What is the speed of the masses after impact?
Correct answer: A. 15 cm s-1
- A. 15 cm s-1
- B. 30 cm s-1
- C. 20 cm s-1
- D. 45 cm s-1
Explanation
The principle of conservation of momentum states that the total momentum before an impact is equal to the total momentum after the impact. In this scenario, both masses are equal and move towards each other, one with a velocity of 60 cm/s and the other with -30 cm/s, due to opposite directions.The equation for conservation of momentum is:m1v1 + m2v2 = (m1 + m2)vSubstituting the values, we have:-30m + 60m = 2mvSolving for v gives v = 15 cm/s.Options B, C, and D are incorrect as they do not reflect this calculation. Each fails to appropriately account for the vector nature of velocity and the correct arithmetic result.
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About Collisions
Collisions involve the conservation of linear momentum when bodies interact for a short time. The topic covers impulse, elastic and inelastic collisions, kinetic energy changes, and the coefficient of restitution, with calculations usually based on one dimensional motion. Momentum remains conserved in isolated collisions, but kinetic energy is conserved only in elastic collisions.
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