Conservative force work over closed path: MCQ with Answer and Explanation

Conservative force work over closed path:
A. Zero
B. Positive
C. Negative
D. Path dependent
Answer: Option A
Solution (By JKExamLibrary)
Conservative forces (gravity, spring): work path-independent ⇒ ∮F·dr = 0 over closed loop. Enables potential energy definition. Memory aid: 'Conservative: ∮F·dr = 0; enables energy conservation'. Mechanics foundation frequently tested in competitive exams.

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Question #1 Report Error
A hydrometer is used to measure
A. Humidity
B. Density of liquids
C. Wind speed
D. Atmospheric pressure

Correct Answer: Option B


Explanation:
Hydrometer measures relative density (specific gravity) of liquids based on floatation principle. Deeper sinking indicates less dense liquid. Hygrometer measures humidity, anemometer wind speed, barometer pressure.

This question belongs to: Science Physics
Question #2 Report Error
Two bodies A and B start from the same point with velocities 10 m/s and 15 m/s respectively in the same direction. If B starts 2 seconds after A, the time after which B catches A is:
A. 8 s
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C. 4 s
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Correct Answer: Option B


Explanation:
When B starts, A has already traveled 10 m/s × 2 s = 20 m. Relative velocity of B w.r.t A = 15 - 10 = 5 m/s. Time to cover 20 m gap at 5 m/s relative speed = 20/5 = 4 s after B starts. Since B started 2 s late, total time from A's start = 2 + 4 = 6 s. Alternatively, equate distances: 10t = 15(t-2) ⇒ 10t = 15t - 30 ⇒ t = 6 s. This relative motion approach simplifies pursuit problems. Memory tip: In same-direction motion, use relative velocity = |v₁ - v₂|. Frequently tested in kinematics sections of competitive exams.

This question belongs to: Science Physics
Question #3 Report Error
An object is placed between pole and focus of a concave mirror. The image is
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Explanation:
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This question belongs to: Science Physics