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

As the train moving in the same direction
Relative velocity ` = v_1 - v_2`
Retardation = a
`v_r = u_r - a_r t`
`rArr t = (v_1 - v_2)/(a)`