This category covers questions on how energy is conserved in physical systems and the role friction plays in energy transfer, resistance, and motion. It includes problems on work, power, and the effects of resistive forces.
For elastic collision, momentum and kinetic energy conserved: m1v1+m2v2=m1v1'+m2v2' and ½m1v1²+... per NCERT. Solving gives velocities matching 6 m/s. Inelastic loses energy. So option A is correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Initial K=12×1000×102=50000J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 4 m/s. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Potential energy mgh=7×10×3=210J. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 210 J. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Work W=F·d=Fd cosθ per NCERT Chapter 6. Positive if force along displacement. Using given F, d, θ, calculation gives 0 J. Work-energy theorem W=ΔK confirms. So option B is correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Kinetic energy K=½mv² and potential U=mgh per NCERT. Energy conservation K+U=constant for conservative forces. Substituting m, v, h gives 180 J as energy, matching option B.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Power P=W/t=F·v per NCERT. Rate of doing work. With given force and velocity, P=Fv. Calculation yields 60 kW. Hence option B correctly represents power.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Work W=F·d=Fd cosθ per NCERT Chapter 6. Positive if force along displacement. Using given F, d, θ, calculation gives -2.9 J. Work-energy theorem W=ΔK confirms. So option B is correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Kinetic energy K=½mv² and potential U=mgh per NCERT. Energy conservation K+U=constant for conservative forces. Substituting m, v, h gives 12 J as energy, matching option A.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Work W=F·d=Fd cosθ per NCERT Chapter 6. Positive if force along displacement. Using given F, d, θ, calculation gives 22 J. Work-energy theorem W=ΔK confirms. So option C is correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Power P=W/t=F·v per NCERT. Rate of doing work. With given force and velocity, P=Fv. Calculation yields 86 kW. Hence option B correctly represents power.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Work W=F·d=Fd cosθ per NCERT Chapter 6. Positive if force along displacement. Using given F, d, θ, calculation gives 54 J. Work-energy theorem W=ΔK confirms. So option B is correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
Work W=F·d=Fd cosθ per NCERT Chapter 6. Positive if force along displacement. Using given F, d, θ, calculation gives 680 J. Work-energy theorem W=ΔK confirms. So option B is correct.
Ref: NCERT Class 11 Physics > Chapter 6: Work, Energy and Power > Topic: Energy Conservation and Friction
