Chapter-5 Work Energy and Power — Online MCQ Test
PHYSICS · Grade 11 · CBSE(NCERT)
Practice Chapter-5 Work Energy and Power with a free chapter-wise online MCQ test.
This chapter covers: Work done by constant and variable forces - Kinetic energy - Work-energy theorem - Potential energy - Conservative and non-conservative forces - Conservation of mechanical energy -....
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Chapter-5 Work Energy and Power — Important Questions & Answers
Work done by a constant force is defined as the product of force, displacement, and the cosine of the angle between them. What is the SI unit of work?
- A. Newton
- B. Joule
- C. Watt
- D. Pascal
Answer: B. Joule
The SI unit of work is Joule (J), which equals Newton-meter (N·m).
The SI unit of work is Joule (J), which equals Newton-meter (N·m).
If a force of 10 N is applied on an object and it moves 5 m in the direction of the force, what is the work done?
- A. 2 J
- B. 15 J
- C. 50 J
- D. 0.5 J
Answer: C. 50 J
Work = Force × Displacement × cos(θ) = 10 × 5 × cos(0°) = 50 J.
Work = Force × Displacement × cos(θ) = 10 × 5 × cos(0°) = 50 J.
A ball is thrown vertically upward with initial velocity 20 m/s. Using the work-energy theorem, find the maximum height reached (g = 10 m/s²).
- A. 10 m
- B. 20 m
- C. 30 m
- D. 40 m
Answer: B. 20 m
Using work-energy theorem: -mgh = 0 - (1/2)mv²; h = v²/(2g) = 400/(2×10) = 20 m.
Using work-energy theorem: -mgh = 0 - (1/2)mv²; h = v²/(2g) = 400/(2×10) = 20 m.
Two objects of mass m₁ and m₂ (m₁ > m₂) are moving with the same kinetic energy. Which has greater momentum?
- A. m₁
- B. m₂
- C. Both have equal momentum
- D. Cannot be determined
Answer: A. m₁
Since KE = p²/(2m), for equal KE, the heavier object has greater momentum: p = √(2m·KE).
Since KE = p²/(2m), for equal KE, the heavier object has greater momentum: p = √(2m·KE).
A force F = 3x² N acts on an object from x = 1 m to x = 3 m. Calculate the work done by this variable force.
- A. 16 J
- B. 24 J
- C. 26 J
- D. 52 J
Answer: C. 26 J
Work = ∫₁³ 3x² dx = [x³]₁³ = 27 - 1 = 26 J.
Work = ∫₁³ 3x² dx = [x³]₁³ = 27 - 1 = 26 J.