Physics MCQs for NEET — Practice Questions with Answers

Example 2.7 states, 'Reaction time depends on complexity of the situation and on an individual.' Therefore, the complexity of the situation directly influences reaction time.

The stopping distance formula is $d_s = \frac{-v_0^2}{2a}$. Here, '$a$' represents deceleration, which is inherently negative. If we consider the magnitude of deceleration, a larger magnitude of 'a' (meaning stronger braking) would lead to a smaller stopping distance because 'a' is in the denominator. The faster you can decelerate, the shorter the distance needed to stop.

The text explicitly states, 'Stopping distance is an important factor considered in setting speed limits, for example, in school zones.' This is because school zones have a higher risk of unexpected pedestrian (children) presence, necessitating shorter stopping distances at lower speeds to prevent accidents.

The Second Law of Thermodynamics states that many conceivable processes that are perfectly allowed by the First Law are never observed. The example given in the NCERT text is: 'A book lying on a table jumping to a height by itself. But such a thing would be possible if the principle of conservation of energy were the only restriction. The table could cool spontaneously, converting some of its internal energy into an equal amount of mechanical energy of the book... But this never happens.' This illustrates that while energy conservation allows it, the Second Law forbids such spontaneous, ordered energy conversion from a colder object to mechanical work.

The Kelvin-Planck statement explicitly says: 'No process is possible whose sole result is the absorption of heat from a reservoir and the complete conversion of the heat into work.' This implies that a heat engine can never have an efficiency of unity (100%).

The Clausius statement explicitly states: 'No process is possible whose sole result is the transfer of heat from a colder object to a hotter object.' This means that heat naturally flows from hot to cold, and to reverse this flow (as in a refrigerator), external work must be done.

The NCERT text states: 'It can be proved that the two statements above are completely equivalent.'

The NCERT text explicitly states: 'In simple terms, it says that efficiency of a heat engine can never be unity. For a refrigerator, the Second Law says that the co-efficient of performance can never be infinite.'

The NCERT summary states: 'Spontaneous processes of nature are irreversible. The idealised reversible process is a quasi-static process with no dissipative factors such as friction, viscosity, etc.' Therefore, spontaneous processes are typically irreversible and associated with dissipative factors.

Option 4 is a statement of the First Law of Thermodynamics (conservation of energy). Options 1, 2, and 3 are direct consequences or statements of the Second Law.