A 5 kg object is moving with 2 m/s. Its momentum is MCQ with Answer and Explanation
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Question #1
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A car accelerates from rest at 2 m/s² for 10 s, then moves with constant velocity for 10 s. Total distance covered is
Question #2
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The time period of oscillation of a spring-mass system in a satellite orbiting Earth is:
Correct Answer: Option A
Explanation:
Spring-mass period T = 2π√(m/k), depending only on mass and spring constant, not on gravity. In orbit, apparent weightlessness doesn't affect spring force (which depends on displacement, not gravity). Thus period remains unchanged. Pendulum period would change (depends on g), but spring-mass does not. Memory aid: 'Spring period: independent of g; pendulum period: depends on g'. This conceptual question tests oscillations fundamentals, frequently examined in competitive exams. Always distinguish gravity-dependent (pendulum) from gravity-independent (spring-mass) oscillators.
Spring-mass period T = 2π√(m/k), depending only on mass and spring constant, not on gravity. In orbit, apparent weightlessness doesn't affect spring force (which depends on displacement, not gravity). Thus period remains unchanged. Pendulum period would change (depends on g), but spring-mass does not. Memory aid: 'Spring period: independent of g; pendulum period: depends on g'. This conceptual question tests oscillations fundamentals, frequently examined in competitive exams. Always distinguish gravity-dependent (pendulum) from gravity-independent (spring-mass) oscillators.
Question #3
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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 B
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.
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