A body `A` starts from rest with an acceleration `a_1`. After `2` seconds, another body `B` starts from rest with an acceleration `a_2`. If they travel equal distances in the `5th` second, after the start of `A`, then the ratio `a_1 : a_2` is equal to :

Options

A. `5 : 9`
B. `5 : 7`
C. `9 : 5`
D. `9 : 7`

Answer

B

Explanation

Distance travelled by body A in 5th second and distance travelled by body B in 3rd second of its motion are equal.
`0+(a_(1))/(2)(2xx5-1)=0+(a_(2))/(2)(2xx3-1)`
`9a_(1)=5a_(2) rArr (a_(1))/(a_(2))=(5)/(9)`