A freely falling body exhibits which type of motion?
A. Uniform acceleration
B. Uniform velocity
C. Zero acceleration
D. Non-uniform acceleration
Answer: Option A
Solution (By JKSSB Mock Tests)
A freely falling body falls under the sole influence of Earth's gravity (neglecting air resistance). Near the surface of the Earth, the acceleration due to gravity ('g') is constant (approximately 9.8 m/s²). Because the acceleration does not change during the fall, it is an example of uniform accelerated motion.
Explanation:
v ∝ 1/√r. If r' = 2r, v' = v/√2. Orbital velocity decreases with increasing radius. Memory aid: 'Higher orbit ⇒ slower speed; v ∝ r⁻¹/²'. Proportional reasoning question testing gravitation formula application, frequently appearing in competitive exams without heavy calculation.
Explanation:
The human ear retains the sensation of sound for about 0.1 seconds (persistence of hearing). To hear a distinct echo, the reflected sound must reach the ear after at least 0.1 s. Distance traveled by sound = Speed × Time = 344 m/s × 0.1 s = 34.4 m. Since this is the total distance (go and return), the minimum distance to the obstacle is 34.4 / 2 = 17.2 meters.
Explanation:
Elastic potential energy stored in a stretched/compressed spring is ½kx², where x is displacement from equilibrium. This is work done against spring force which is average force times displacement. Work = ½Fx = ½(kx)x = ½kx². Similar to capacitor energy ½CV².
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