Question

Two particle of masses in the ration 1:2 with charges in the ratio 1:1, are palced at rest in a uniform electric field. They are relesaded and allowed to move for the same time. The ratio of their kinetic energies will be finally
A. `2:1`
B. `8:1`
C. `4:1`
D. `1:4`

Answer 1

Correct Answer - A
As charge on both particles is same. So electric force action on them will be same. Since the particles are allowed to move for the same time, their final momentun will be same. Because change in momintum = impulse = forcexxtime, so
`KE=(P^2)/(2m)` gives `KE prop (1)/(m)`
`(KE_(1))/(KE_(2))=(m_(2))/(m_(1))=2:1`.