In a perfectly elastic collision between two bodies, which of the following physical quantities are conserved?
A. Only momentum
B. Both momentum and kinetic energy
C. Neither momentum nor kinetic energy
D. Only kinetic energy
Answer: Option B
Solution (By JKSSB Mock Tests)
In any collision (elastic or inelastic), the total linear momentum is always conserved, provided no external forces act on the system. However, a perfectly elastic collision is specifically defined as one in which there is absolutely no loss of kinetic energy. Therefore, both total linear momentum and total kinetic energy are conserved.
Two waves of identical frequency and amplitude superimpose in the same medium. If they meet perfectly in phase (crest meets crest), the resulting amplitude is:
Explanation:
This is an example of constructive interference. According to the principle of superposition, the resultant displacement is the algebraic sum of individual displacements. If the waves are perfectly in phase, their amplitudes add directly (A + A = 2A). Note that while amplitude doubles, the intensity (which is proportional to amplitude squared) becomes four times greater.
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