Which of the following graphs represents a body at rest?
A. Displacement-time graph parallel to time axis
B. Velocity-time graph with zero slope
C. Displacement-time graph with constant positive slope
D. Velocity-time graph with positive slope
Answer: Option A
Solution (By JKSSB Mock Tests)
For a body at rest, displacement remains constant over time. The displacement-time graph is a horizontal line, parallel to time axis, indicating zero slope (velocity = 0). Option A indicates constant velocity. Option B (velocity-time zero slope) means constant velocity, not necessarily rest (could be constant non-zero velocity). Option D indicates acceleration. So C is correct.
Explanation:
Speed = distance/time = 100 m / 5 s = 20 m/s. Convert to km/h: multiply by 18/5 => 20 × 18/5 = 72 km/h. Pole is a point, so train's own length is the distance crossed. Speed in km/h = m/s × (18/5). 20 × 18/5 = 72.
Explanation:
The time period of a simple pendulum is given by T = 2π√(L/g), where L is the length of the string and g is acceleration due to gravity. The time period is directly proportional to the square root of the length (T ∝ √L). If L becomes 4L, the new time period T' = √4 = 2 times the original. It doubles.
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