Question
Physics Question on Atoms
An H -atom moving with speed v makes a head-on collision with another H -atom at rest. Both the atoms are in the ground state. The minimum value of velocity v for which one of the atoms may excite is
A
6.25×104ms−1
B
8×104ms−1
C
7.25×104ms−1
D
13.6×104ms−1
Answer
6.25×104ms−1
Explanation
Solution
For vmin collision should be completely inelastic. According to energy conservation principle, ∴21mvmin2=21mv2+21mv2+ΔE ...(i)) According to momentum conservation principle. mvmin=mv+mv ∴v=2mmin ...(ii) After solving e (i) an d(ii), we get 21mvmin2=2ΔE ∴vmin=(m4ΔE) Here, ΔE= minimum excitation energy =10.2eV m=1.67×10−27kg ∴vmin=(1.67×(10)−274×10.2×1.6×(10)−19) =6.25×104ms−1