The efficiency of a Carnot engine depends on: MCQ with Answer and Explanation
Question
Report Error
Discuss this Question (0)
Practice More Physics Questions
Question #1
Report Error
A body floats in a liquid with one-third of its volume above the surface. The density of the body relative to the liquid is:
Correct Answer: Option D
Explanation:
By Archimedes' principle, weight of body = weight of displaced liquid. Let V be total volume, ρ_b body density, ρ_l liquid density. Volume submerged = (2/3)V. Thus ρ_b·V·g = ρ_l·(2V/3)·g ⇒ ρ_b/ρ_l = 2/3. Fraction submerged equals density ratio. Memory tip: 'Fraction submerged = ρ_object / ρ_fluid'. This direct application of floatation condition is common in competitive exams. Always identify submerged fraction correctly: here 'one-third above' means two-thirds submerged. Such problems test conceptual clarity in buoyancy applications.
By Archimedes' principle, weight of body = weight of displaced liquid. Let V be total volume, ρ_b body density, ρ_l liquid density. Volume submerged = (2/3)V. Thus ρ_b·V·g = ρ_l·(2V/3)·g ⇒ ρ_b/ρ_l = 2/3. Fraction submerged equals density ratio. Memory tip: 'Fraction submerged = ρ_object / ρ_fluid'. This direct application of floatation condition is common in competitive exams. Always identify submerged fraction correctly: here 'one-third above' means two-thirds submerged. Such problems test conceptual clarity in buoyancy applications.
Question #2
Report Error
A car travels from point A to B with speed 40 km/h and returns from B to A with speed 60 km/h. The average speed for the entire journey is:
Correct Answer: Option C
Explanation:
Average speed = Total distance / Total time. Let distance AB = d km. Time for AB = d/40 h, time for BA = d/60 h. Total distance = 2d km. Total time = d/40 + d/60 = d(3+2)/120 = 5d/120 = d/24 h. Average speed = 2d / (d/24) = 48 km/h. Note: Average speed is not arithmetic mean of speeds (which would be 50 km/h) because time intervals differ. This harmonic mean concept is crucial for motion problems. Exam tip: For equal distances, average speed = 2v₁v₂/(v₁+v₂). Frequently tested in competitive exams.
Average speed = Total distance / Total time. Let distance AB = d km. Time for AB = d/40 h, time for BA = d/60 h. Total distance = 2d km. Total time = d/40 + d/60 = d(3+2)/120 = 5d/120 = d/24 h. Average speed = 2d / (d/24) = 48 km/h. Note: Average speed is not arithmetic mean of speeds (which would be 50 km/h) because time intervals differ. This harmonic mean concept is crucial for motion problems. Exam tip: For equal distances, average speed = 2v₁v₂/(v₁+v₂). Frequently tested in competitive exams.
Question #3
Report Error
Mercury is used in thermometers because it
No comments yet. Be the first to start the discussion!