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Rotational Motion Applications

Practice questions covering torque, angular momentum, and rotational dynamics with real-world applications. Focuses on problem-solving techniques for physics exams.

25 questions

Rotational Motion Applications

Why can a rigid body not deform under the influence of forces in theoretical mechanics?

In theoretical mechanics, a rigid body is an idealization where inter-particle distances are fixed, preventing deformation and allowing focus on rotational and translational motion only. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Because it is an idealization with fixed distances. 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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Rotational Motion Applications

Which physical quantity is defined as r×p for a particle?

Angular momentum of a particle is defined as L = r×p, where r is the position vector and p is the linear momentum. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Angular momentum. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

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

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Rotational Motion Applications

Three particles of masses 1kg, 5kg, and 10kg are at (0,2), (3,0), and (4,6) respectively. What is the x-coordinate of th

Formula: X = m1x1+m2x2+m3x3m1+m2+m3. Masses: 1,5,10kg; x-coordinates: 0,3,4. X = (1×0)+(5×3)+(10×4)1+5+10 = 0+15+4016 = 5516≈3.44m. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 3.44 m. 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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Rotational Motion Applications

What is the condition for a rigid body to have zero angular acceleration?

Angular acceleration is zero when the net torque is zero (τ = Iα), as torque drives rotational change. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Net torque is zero. 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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Rotational Motion Applications

A solid sphere of mass 3kg and radius 0.4m rotates about its center at 5rad/s. What is its rotational kinetic energy?

I = 25MR2 = 25×3×(0.4)2 = 0.192kg m2. K = 12Iω2 = 12×0.192×(5)2 = 0.096×25 = 2.4J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 2.4 J. 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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Rotational Motion Applications

Three particles of masses 3kg, 6kg, and 9kg are located at (0,1), (2,2), and (4,0) respectively. What is the x-coordinat

Formula: X = m1x1+m2x2+m3x3m1+m2+m3. Masses: 3,6,9kg; x-coordinates: 0,2,4. X = (3×0)+(6×2)+(9×4)3+6+9 = 0+12+3618 = 4818 = 2.67m. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 2.67 m. 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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Rotational Motion Applications

A 6kg object moves with a velocity of 3i^−2j^m/s. What is the magnitude of the velocity of its center of mass?

For a single object, the center of mass velocity equals the object’s velocity. Magnitude = (3)2+(−2)2 = 9+4 = 13≈3.6m/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 3.6 m/s. 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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Rotational Motion Applications

What is the SI unit of moment of inertia?

Moment of inertia I = ∑miri2 has units of mass times distance squared, so the SI unit is kg m2. As per NCERT, applying relevant law/formula with correct units and sign convention leads to kg m². 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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