NEET Practice Questions (MCQs) with Answers & Solutions

The 'POINTS TO PONDER' section states: 'For linear simple harmonic motion with a given $ \omega $, two initial conditions are necessary and sufficient to determine the motion completely. The initial conditions may be (i) initial position and initial velocity or (ii) amplitude and phase or (iii) energy and phase.'

The 'POINTS TO PONDER' section clearly states: 'The period of SHM does not depend on amplitude or energy or the phase constant. Contrast this with the periods of planetary orbits under gravitation (Kepler’s third law).'

From the 'SUMMARY' section: 'The angular frequency $ \omega $ is related to the period and frequency of the motion by, $ \omega = 2\pi / T = 2\pi \nu $ (angular frequency).'

The NCERT text states: 'In practice, oscillating bodies eventually come to rest at their equilibrium positions because of the damping due to friction and other dissipative causes.' This describes damped oscillations.

Problem 13.1 from the exercises asks to identify periodic motions. An arrow released from a bow follows a parabolic trajectory but does not repeat its motion at regular intervals, making it non-periodic. The other options describe motions that repeat after a certain time.

The 'POINTS TO PONDER' section states: 'The motion of a simple pendulum is simple harmonic for small angular displacement.' For large angles, the motion is still periodic but not simple harmonic.

Point 6 from 'POINTS TO PONDER' states: 'A combination of two simple harmonic motions with arbitrary amplitudes and phases is not necessarily periodic. It is periodic only if frequency of one motion is an integral multiple of the other’s frequency. However, a periodic motion can always be expressed as a sum of infinite number of harmonic motions with appropriate amplitudes.' This decomposition of a general periodic function into a sum of harmonic functions is known as Fourier analysis, where the frequencies will typically be integer multiples of a fundamental frequency.

During the S phase, DNA replication occurs, so the DNA content doubles from 2C to 4C, but the chromosome number remains 2n because sister chromatids are still joined. In M phase (mitosis), the sister chromatids separate and are distributed to daughter cells. Therefore, each daughter cell (and thus the cell at the end of M phase) will have 2n chromosomes and 2C DNA content, identical to the parent cell in G1. Mitosis is an equational division where the chromosome number in parent and progeny cells remains the same.

If the DNA content after the M phase (i.e., in a daughter cell in G1) is 2C, then during the S phase, DNA replication doubles the content. Therefore, at G2 phase, the DNA content will be 4C. The question provided in the NCERT text states: 'Also, what will be the DNA content of the cells at G1, after S and at G2, if the content after M phase is 2C?' This implies that the '2C' after M phase refers to the baseline content for a diploid cell in G1. Thus, G2 will have 4C.

During G1, the DNA content is C and chromosome number is 2n. After S phase, DNA replication occurs, doubling the DNA content to 2C, but the number of chromosomes remains 2n (as each chromosome now consists of two sister chromatids). Prophase follows the S and G2 phases, so an early prophase cell will have already completed DNA replication. Therefore, the DNA content will be 2C, and the chromosome number will still be 2n.