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#physics explanation

9 public questions tagged with this topic.

Surface Tension, Capillarity and Excess Pressure

Why does the viscosity of liquids generally decrease with increasing temperature?

Higher temperatures increase molecular kinetic energy in liquids, weakening intermolecular forces, reducing resistance to flow, and thus lowering viscosity, as noted in the chapter. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Intermolecular forces weaken. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Gravitational Effects and Applications

Why does an object require more energy to escape from a higher altitude than to reach that altitude?

Escape energy from altitude h is GMmR+h, while energy to reach h from the surface is GMm(1R−1R+h), which is less. Escape requires overcoming all potential energy to infinity. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Escape needs energy to infinity. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: Halliday & Resnick, Fundamentals of Physics, 11th ed., Chapter 13: Gravitation.

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Escape Velocity and Bound Systems

Why does the gravitational potential energy approach zero as the distance between two masses increases?

V = −GMmr, with the convention that V = 0 at r→∞. As r increases, 1r decreases, making V less negative and approaching zero. As per NCERT, applying relevant law/formula with correct units and sign convention leads to It is defined as zero at infinity. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: Halliday & Resnick, Fundamentals of Physics, 11th ed., Chapter 13: Gravitation.

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