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Q4.12: NCERT Physics - Part 1 LAWS OF MOTION 4.12 Solution: A bob of mass 0.1 kg hung from the ceiling of a room by a…
⚠️ Common Exam Traps & Conceptual Pitfalls
Students often assume the bob’s motion after the string is cut follows the line of the string; in reality it retains its instantaneous *tangential* velocity. Thus at an extreme point the speed is zero and the bob falls straight down, while at the mean position the velocity is horizontal, producing a projectile parabola.
A bob of mass 0.1 kg hung from the ceiling of a room by a string 2 m long is set into oscillation. The speed of the bob at its mean position is 1 m s__. What is the trajectory of the bob if the string is cut when the bob is (a) at one of its extreme positions, (b) at its mean position.
Step-by-Step Verified Solution
**Answer:** (a) Vertical straight line (free fall) (b) Parabolic path
**Step-by-Step Explanation:**
(a) At extreme position, velocity of bob is zero. When string is cut, the bob falls vertically under gravity [citation:10].
(b) At mean position, bob has horizontal velocity of 1 m/s. When string is cut, it becomes a projectile with initial horizontal velocity and falls under gravity, following a parabolic path [citation:10].
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