Verified Solution • 2025–26 Session moderate

Q5.12: NCERT Physics - Part 1 WORK, ENERGY AND POWER 5.12 Solution: An electron and a proton are detected in a cosmic ray…

An electron and a proton are detected in a cosmic ray experiment, the first with kinetic energy 10 keV, and the second with 100 keV. Which is faster, the electron or the proton? Obtain the ratio of their speeds. (electron mass = 9.11_10___ kg, proton mass = 1.67_10___ kg, 1 eV = 1.60_10___ J).

Step-by-Step Verified Solution

**Answer:** Electron is faster. Ratio v_e/v_p = 13.5 **Step-by-Step Explanation:** Kinetic energy: K = _mv_, so v = �(2K/m). For electron: K_e = 10 keV = 10 _ 10_ _ 1.6 _ 10___ = 1.6 _ 10___ J.
ve=2×1.6×10−159.11×10−31=5.93×107 m/sv_e = \sqrt{\frac{2 \times 1.6 \times 10^{-15}}{9.11 \times 10^{-31}}} = 5.93 \times 10^7 \text{ m/s}
For proton: K_p = 100 keV = 1.6 _ 10___ J.
vp=2×1.6×10−141.67×10−27=4.38×106 m/sv_p = \sqrt{\frac{2 \times 1.6 \times 10^{-14}}{1.67 \times 10^{-27}}} = 4.38 \times 10^6 \text{ m/s}
Ratio = 5.93 _ 10_ / 4.38 _ 10_ = 13.5.

All Questions in this Chapter

Q5.1 Q5.2 Q5.3 Q5.4 Q5.5 Q5.6 Q5.7 Q5.8 Q5.9 Q5.10 Q5.11 Q5.12 Q5.13 Q5.14 Q5.15 Q5.16 Q5.17 Q5.18 Q5.19 Q5.20 Q5.21 Q5.22 Q5.23

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