A car moving at 72 km/h is brought to rest in 10 seconds. The deceleration is
A. 2.5 m/s²
B. 20 m/s²
C. 2 m/s²
D. 7.2 m/s²
Answer: Option C
Solution (By JKExamLibrary)
72 km/h = 72 × (5/18) = 20 m/s. Initial velocity u = 20 m/s, final v = 0, t = 10 s. Using v = u + at => 0 = 20 + a×10 => a = -2 m/s², so deceleration magnitude is 2 m/s². Conversion factor 5/18 is essential: multiply km/h by 5/18 to get m/s.
Explanation:
The total energy of an electron in a hydrogen-like atom in the nth orbit is strictly negative and given by the mathematical formula E_n = -13.6 Z^2 / n^2 (in eV). This formula demonstrates that the total energy is inversely proportional to the square of the principal quantum number (n^2).
Explanation:
According to Gauss's Law in electrostatics, all excess charge on a conducting body resides entirely on its outer surface. Since there is no net charge enclosed within the hollow interior, the electric flux and consequently the electric field everywhere inside the hollow conducting sphere is exactly zero.
Explanation:
Convert speeds: 18 km/h = 5 m/s, 36 km/h = 10 m/s. Using v = u + at => a = (10-5)/5 = 1 m/s². Distance s = ut + ½at² = 5×5 + ½×1×25 = 25 + 12.5 = 37.5 m. Also using average velocity: (5+10)/2 × 5 = 7.5×5 = 37.5 m. Answer A.
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