ExamsMy practice
A positive ion A and a negative ion B has charges 6.67 10-19 C and 9.6 10-10 C, and masses 19.2 10-27 kg and 9 10-27 kg respectively. At an instant, the ions are separated by a certain distance r. At that instant the ratio of the magnitudes of electrostatic force to gravitational force is P 10-13, where the value of P is . (Take 14 0=9 109 Nm2C-2 and universal gravitational constant as 6.67 10-11 Nm2 kg-2 )
Answer
BONUS
Solution
Concept: both forces vary as 1r2, so r cancels in the ratio.
FeFg= 14 0 qAqBG mAmB
= 9 109 6.67 10-19 9.6 10-106.67 10-11 19.2 10-27 9 10-27
Cancel 6.67 and 9; 9.619.2=0.5
⇒ FeFg=0.5 10(9-19-10)-(-11-27-27)=0.5 10-20+65
=5 1044
⇒ P 10-13=5 1044 ⇒ P=5 1057
The printed values of the charge and masses do not lead to a meaningful value of P of the form asked, so this question is treated as Bonus.
Answer: Bonus