An express train is moving with a velocity `v_1`. Its driver finds another train is movig on the same track in the same direction with velocity `v_2`. To escape collision, driver applies a retardation a on the train. The minimum time of escaping collision be

Options

A. `t=(v_(1)-v_(2))/a`
B. `t=(v_(1)^(2)-v_(2)^(2))/2`
C. None
D. Both

Answer

A

Explanation

`v_(1//2)=(v_(1)-v_(2))`
`0=v_(1//2)-atimplies (v_(1)-v_(2))/a`